The Class A amplifier - build and test (2/2)

Summary

In this educational video, the creator discusses designing, simulating, and building a single-transistor wideband common emitter amplifier. The goal is to deliver half a watt into a 50-ohm load using a BD135 NPN transistor. The video covers the calculation of components, biasing, and efficiency, followed by real-life testing to verify performance. The creator also uses a circuit simulator to ensure accuracy and discusses the amplifier's wide bandwidth and modulation capabilities. The video concludes with a thermal performance test and insights on improving efficiency.

Takeaways

• 🔬 The video focuses on designing, simulating, and building a Class A single-transistor wideband common emitter amplifier.
• 🎯 The design goal is to deliver half a watt into a 50-ohm load, using a BD135 medium power NPN transistor for amplification.
• 🔧 The amplifier configuration includes a resistor network for bias point setting, an emitter resistor for stability and negative feedback, and an inductor in the collector for efficiency.
• 🔌 The supply voltage is calculated to be 10 volts, considering the load, collector-emitter voltage drop, and emitter resistor voltage drop.
• 🔢 The static operating current is determined to be 141.5 milliamps, which is half of the peak current.
• ⚙️ The emitter resistor is calculated to be 3.3 ohms, and the biasing resistors are calculated to be 620 ohms and 91 ohms.
• 🌡️ The amplifier is expected to have a power dissipation of almost 1.5 watts, necessitating a heatsink for the transistor.
• 📊 Simulations show a voltage gain of about 13, an efficiency of 28.6%, and a bandwidth from 10 kHz to 10 MHz.
• 🔍 Real-life testing confirms the amplifier's performance, with a wide bandwidth and good modulation following for various types of signals.
• 🌡️ Thermal performance testing indicates the importance of considering heat dissipation not only for the transistor but also for other components.

Q & A

What is the main goal of designing the class A amplifier discussed in the script?

The main goal is to design a single transistor wideband common emitter amplifier that can deliver half a watt into a 50-ohm load.

Why is a BD135 transistor chosen as the main amplifying element?

The BD135 is chosen because it is a medium power NPN transistor with a high enough transition frequency to allow the amplifier to work up to a few megahertz.

What is the expected theoretical maximum efficiency of the amplifier design?

The expected theoretical maximum efficiency of the amplifier design is 50%.

How is the output voltage calculated for the amplifier?

The output voltage is calculated based on the output load value and the output power, requiring a 5-volt RMS voltage, which translates to a 14.14-volt peak-to-peak voltage.

What is the purpose of the emitter resistor in the amplifier circuit?

The emitter resistor serves two purposes: it helps set the voltage gain of the circuit and provides a voltage drop that contributes to heat dissipation and circuit stability.

Why is an inductor placed in the collector of the amplifier?

An inductor is placed in the collector to maximize efficiency by minimizing the voltage drop across the collector and emitter.

How is the static operating current determined for the amplifier?

The static operating current is determined based on the peak-to-peak load voltage and the load value, which gives a peak current of 283 milliamps, and the static current is half of this value.

What is the significance of the biasing resistors in the circuit?

The biasing resistors are used to set the operating point of the transistor and ensure stability by providing the right amount of base current.

How is the power dissipation calculated for the transistor?

The power dissipation is calculated by considering the static power consumption of the amplifier, which is assumed to be mostly dissipated on the transistor, resulting in almost one and a half watts.

What is the expected efficiency of the amplifier based on simulations?

The expected efficiency based on simulations is about 35%, which is derived from the output power and the input power calculations.

How is the bandwidth of the amplifier tested and what are the results?

The bandwidth is tested using an AC simulation, and the results show a flat response from around 10 kHz up to around 10 MHz, indicating a wide bandwidth amplifier.

Outlines

00:00

🔬 Designing a Class A Amplifier

The speaker introduces the project of designing, simulating, and building a single-transistor wideband common emitter amplifier. The goal is to deliver half a watt into a 50-ohm load using a BD135 transistor. The design includes a common emitter configuration with a resistor network for biasing, an emitter resistor for stability and negative feedback, and an inductor in the collector for efficiency. The speaker outlines the calculations for determining the required supply voltage, static operating current, and resistor values, aiming for a theoretical efficiency of 50%. The design omits impedance matching to achieve a wide bandwidth frequency response.

05:01

🧮 Calculating Component Values

The speaker delves into the calculations for the amplifier's components. They determine the necessary output voltage and supply voltage, taking into account the load, collector-emitter voltage drop, and voltage drop across the emitter resistor. The static operating current is calculated based on the peak load voltage and load value. The emitter resistor value is derived from the desired voltage drop and peak current, with a slight adjustment to a standard value. The biasing resistors are calculated based on the voltage drops and currents, with the speaker opting for standard resistor values. Power dissipation is also considered, leading to the recommendation of a heatsink for the transistor.

10:03

📡 Testing the Amplifier Circuit

The speaker tests the designed amplifier circuit using a circuit simulator. They verify the static operating point and compare the simulated collector current with the calculated values. The simulator is also used to test the circuit at different temperatures to mimic real-world operating conditions. The speaker checks the output signal, efficiency, voltage gain, and harmonics using the simulator. They find that the efficiency is slightly lower than expected, and the voltage gain is less than calculated due to the transistor's internal resistance. An AC simulation confirms a wide bandwidth from 10 kHz to 10 MHz.

15:04

🔍 Real-life Testing and Observations

The speaker assembles the amplifier circuit and tests it in real life. They measure the current consumption, which increases as the transistor warms up, and observe the output signal's amplitude and distortion at different input levels. The frequency response is tested, showing a wide bandwidth from 10 kHz to 5 MHz. The speaker performs modulation tests, including amplitude, phase, and frequency shift keying, demonstrating the amplifier's ability to handle various types of signals. Thermal performance is also evaluated, with the transistor and some resistors heating up during operation.

20:05

🔋 Efficiency and Future Considerations

The speaker discusses the efficiency of the Class A amplifier, noting that it is limited by non-ideal elements such as the collector-emitter voltage drop and the emitter resistor voltage drop. They suggest that using higher supply voltages with correct impedance matching could improve efficiency. The speaker highlights the high linearity and simplicity of the Class A amplifier, making it suitable for various applications, especially in audio and radio frequency signal amplification. They conclude by hinting at potential improvements or alternatives to the Class A design.

Keywords

💡Class A Amplifier

A Class A amplifier is a type of linear amplifier that operates in a mode where the output stage is always active, regardless of the input signal. This means it does not switch on and off, which results in high linearity and low distortion. In the video, the creator is designing a single-transistor wideband common emitter amplifier, which is a specific configuration of a Class A amplifier. The goal is to deliver half a watt into a 50-ohm load, showcasing the practical application of a Class A amplifier in achieving a specific power output with minimal distortion.

💡Common Emitter Configuration

The common emitter configuration is a basic transistor amplifier circuit where the emitter terminal is common to both the input and output circuits. This configuration is widely used due to its versatility and ability to provide voltage amplification. In the script, the creator mentions using a common emitter amplifier configuration with a resistor network to set the bias point and an emitter resistor for stabilization, which is a typical approach in designing such amplifiers.

💡Bias Point

The bias point, also known as the operating point, is the DC voltage and current at which a transistor operates in a circuit. Setting the correct bias point is crucial for the stability and performance of an amplifier. In the video script, the creator calculates the necessary components to set the bias point, ensuring that the transistor operates within its linear region to achieve the desired amplification without distortion.

💡Emitter Resistor

An emitter resistor is used in a transistor amplifier circuit to provide negative feedback, which helps stabilize the gain and improve the linearity of the amplifier. It also plays a role in dissipating heat, which is important for the thermal management of the circuit. The video script describes calculating the value of the emitter resistor based on the desired voltage drop and the peak current, which is a key step in designing the amplifier.

💡Collector Inductor

A collector inductor is a component placed in the collector circuit of a transistor amplifier to improve efficiency by maximizing the power transfer to the load. It helps in achieving a higher theoretical efficiency by minimizing the losses in the circuit. The script mentions that more inductance generally allows the amplifier to handle lower frequencies, which is an important consideration in the design of wideband amplifiers.

💡DC Isolation Capacitors

DC isolation capacitors are used in amplifier circuits to block DC voltages while allowing AC signals to pass through. They are essential in preventing DC voltage from affecting the operation of the input signal source and the output load. In the video, the creator includes input and output DC isolation capacitors to isolate the signal source and load, ensuring that the amplifier functions correctly without introducing DC offsets.

💡Supply Voltage

The supply voltage is the voltage provided to the power supply of an electronic circuit. It is a critical parameter that affects the performance and efficiency of the circuit. In the script, the creator calculates the required supply voltage based on the output load, the minimum collector-emitter voltage drop, and the voltage drop across the emitter resistor, which is essential for ensuring the amplifier operates within its specified parameters.

💡Static Operating Current

The static operating current is the current that flows through a circuit when there is no input signal, representing the quiescent current of the amplifier. It is an important parameter for calculating power consumption and heat dissipation. The video script describes calculating the static operating current as half of the peak current, which is a standard practice in amplifier design to ensure stable operation.

💡Voltage Gain

Voltage gain is the ratio of the output voltage to the input voltage in an amplifier, a measure of how much the amplifier increases the voltage level of the signal. The creator calculates the expected voltage gain based on the load value and the emitter resistor, which is a key factor in determining the overall amplification capability of the amplifier. The script also mentions that the actual gain may be slightly lower due to the equivalent resistance in the transistor's emitter.

💡Efficiency

Efficiency in the context of an amplifier refers to the ratio of the output power to the input power, indicating how effectively the amplifier converts input power into output power. The script discusses the calculated efficiency of the amplifier, which is around 35 percent, and compares it to the theoretical maximum efficiency of 50 percent for a Class A amplifier. The creator also suggests that efficiency could be improved by using higher supply voltages, which is an important consideration in amplifier design.

Highlights

Introduction to designing a single transistor wideband common emitter amplifier

Design goal to deliver half a watt into a 50 ohm load

Selection of BD135 medium power NPN transistor for its high transition frequency

Schematic overview including bias point setting and gain stabilization

Calculation of required 5 volt RMS output voltage for the amplifier

Determination of supply voltage considering collector-emitter voltage drop and emitter resistor voltage

Calculation of static operating current and its significance in amplifier design

Emitter resistor calculation based on set voltage drop and peak current

Biasing resistors calculation to ensure stability and desired current flow

Power dissipation estimation and the need for a heatsink

Expected efficiency calculation based on output and input power

Circuit simulation to verify calculations and operating point

Testing the amplifier's performance in real life with a compact design

Observation of current consumption and its relation to transistor temperature

Analysis of signal distortion at different input signal amplitudes

Frequency response test showing a wide bandwidth up to 20 megahertz

Modulation performance test including amplitude, phase, and ASK

Thermal performance measurement and the importance of considering all components' heat dissipation

Discussion on improving efficiency through higher supply voltages and impedance matching

Conclusion on the amplifier's high linearity and simplicity, suitable for various applications

Transcripts

hello

and welcome back

today i want to continue talking about

the class a amplifier by designing

simulating and building a single

transistor wideband common emitter

amplifier i mean how hard can it be

anyway

afterwards of course i will be testing

the circuit out to verify its actual

performance

like how linearly does it follow an

input signal and just how hot does it

get

and if you're curious then keep watching

[Music]

so first things first what is the design

goal

well as with all the linear amplifiers

that i will be building in this mini

series i want to deliver half a watt

into a 50 ohm load

since as a test load i will be using a

termination resistor

and if i'm delivering more power i'm

afraid i might break it

and as main amplifying element i will be

using a bd135

medium power npn transistor that should

have a high enough transition frequency

to allow the amplifier to work up to a

few megahertz

so let's start calculating the

components

now the general schematic will look

something like this

so i will be using a common emitter

amplifier configuration with a resistor

network to set the bias point and an

emitter resistor to stabilize the gain

and provide negative feedback

finally an inductor will be placed in

the collector to maximize efficiency so

this general topology should allow a

maximum theoretical efficiency of 50

and finally we will have input and

output

dc isolation capacitors

to isolate the input signal source and

the output load

and a supply voltage now i won't be

using any impedance matching

first of all to keep things simple but

also to get the wide bandwidth frequency

response

so to start calculating the components

let's start with what we actually know

so knowing the output load value and the

output power we can work out the output

voltage that we need

so we will need the 5 volt rms voltage

which translates to a 14 point 14 volt

peak to peak voltage now even though

this configuration

can supply double the supply voltage on

the output we will need a bit more than

7 volts to supply the circuit so the

supply voltage will have to be half of

the output load peak to peak voltage but

we also need to account for the minimum

collector emitter voltage drop and the

voltage that's dropping on the emitter

resistor

at peak current so to work out the

actual supply voltage we will need 7

volts for the load for the collector

emitter voltage we can take a value of 2

volts since the data sheet does provide

dc current gains at this specific value

so we'll choose this and for the emitter

resistor well this component has two

purposes

on the one side based on this component

and the load value we can set the

voltage gain of the circuit but secondly

the larger the voltage drop that occurs

on this resistor well the more heat gets

dissipated but also the exact base

emitter voltage which is temperature

dependent becomes less important in

analyzing the stability of the circuit

so by having large emitter resistor

voltages we can make the circuit more

stable

so we'll set this voltage drop to 1 volt

so the total supply voltage will end up

being 10 volts next we need to calculate

the static operating current so the

point around which the current will

oscillate as the amplifier is amplifying

and well this needs to be half of the

peak current

so we need to work out that thing first

so this can be determined based on the

peak to peak load voltage and well the

load value and this gives us a peak

current of 283 milliamps

so knowing this

we can work out the static current which

is half of this so

141.5 milliamps

now we can start working on the

components of the circuit so first

let's start off with the emitter

resistor

and we can calculate this based on the

voltage drop that we've set of 1 volt

and the peak current of 283 so this

gives us a value of 3.53 ohms

now

this isn't really a standard value so

i'll be using a resistor of 3.3 ohm

since i actually have this component

based on this value and the load we can

now work out the

expected voltage gain so based on the

load value and the emitter resistor this

gives us a voltage gain of 15

but in reality we'll be getting slightly

lower gains because of the equivalent

resistor present in the emitter of the

transistor so we don't just have the

emitter resistor on the outside we also

have a small resistor inside of the

transistor finally we can start working

on the biasing resistors

so first let's work out the exact

voltage drops on each of these so first

the voltage drop on r1 this will be

equal to the voltage dropping on the

emitter resistor plus the voltage

dropping on the base emitter junction

so we can take a base emitter voltage of

0.7 volts

and for the emitter resistor we can work

out the voltage drop based on the static

current so we're getting a total voltage

drop on r1 of 1.16 volts

now the voltage drop on r2

is well the supply of voltage minus

whatever is dropping on r1 so we get

8.84

next we need to work on the currents

and the first thing too calculate is the

base current of the main transistor

so this is calculated based on the

collector current and the gain factor so

for the exact transistor that i'll be

using i have a minimum gain

of about 100 and the static collector

current is 141 milliamps so this gives

us a base current of 1.41 milliamps now

to ensure stability in the circuit

common way of calculating the two

resistors is to set the current going

through r2 that is 10 times the base

current

and well the current going through r1 is

nine times the base current so one times

goes through the base so by this logic

we can work out that r2 will have a

current of 14.1 milliamps

and the current through r1 will be 12.7

now we know the currents we know the

voltages so we can work out the actual

resistor values

and again we're getting non-standard

values

so i'll be using a 620 ohm resistor and

a 91 ohm resistor for the two

bias setting resistors

final thing we can do is calculate the

power dissipation so since the amplifier

will consume roughly the same amount of

power whether it's doing something or

not we should calculate how much power

is being used in a static point and we

can assume that most of this power is

dissipated on the transistor so we're

getting almost one and a half watts so

definitely we should have a heatsink to

make sure that the transistor doesn't

self-destruct final thing to do we can

work out the expected efficiency

so we know the output power of half watt

we know the input power of 1.41 watts

and this gives us an efficiency of about

35 percent

so it's not 50 but it's not that bad

either so finally just to make sure that

no errors were made during these

calculations

let's check the circuit in a circuit

simulator

so here is the circuit that we've just

calculated

now i added in the various resistor

values that we've worked on

and

as transistor model

i used one that i found online

so i found this website that's somehow

related to philips

philips being one of the manufacturers

that used to produce this transistor in

the past and the nice thing about this

website is that they are providing a

model for the bd155-16

so this is a specific gain group and

this is the transistor from which i have

the practical one so i'll be using this

model and i'll be leaving a link to this

in the description so if you want to

check this website out so now back to

the circuit first thing to check is the

static operating point that's why

there's no input or output signal here

if we run the circuit we can check the

current running through the collector

which is around 130 milliamps slightly

lower than what we've calculated and

other than this current the total

current passing through the circuit is

about 144 milliamps now regarding the

current consumption it's important to

point out that the current simulation is

running at 25 degrees celsius but we can

also simulate at another temperature say

60

because the class a amplifier will heat

up in its operation so we can expect the

transistor to be a bit hotter

so if we now look at the collector

current we can see that the 130

milliamps is

the behavior at 25 degrees

but there's also a nice blue line up

here at around 142 milliamps which is at

60 degrees

so the hotter the transistor will be

running

the higher the collector current now

other than waiting for the transistor to

heat up

another thing that we could do is

increase the value of

r1 but for the moment i'll leave things

as they are

so the higher the current at which the

transistor is running

the lower the gain it will have so

that's why i'm leaving the circuit as it

is

but now i'll leave the temperature at 60

and if we now add in all of the other

components so other than the main

amplifier an input signal

coupling capacitors both on the input

and output load and

the inductor

now without going into too many details

about these other components regarding

the collector inductor

more is better in general so the more

inductance this inductor has the lower

the frequencies that the amplifier will

be able to handle

now on the other hand a very large

inductor will also have a lot of

parallel capacitance so there's a

balance that needs to be found here

similar story with the coupling

capacitors larger is better the larger

the capacitor the lower the bandwidth is

pushed to low frequencies

so anyway

if we run the circuit

we can look at the voltage present in

the collector

we can see that for the specific signal

that i'm inputting it's dropping to

almost three volts and the voltage on

the emitter resistor

is rising up to about 925 so we're

getting about two point something volts

drop on the collector emitter of the

transistor

we can also look at the signal on the

output so it's almost

14 volts peak to peak

and this is giving us an output power of

about 450 milliwatts so slightly lower

than 500 but it will do

and we can also perform some automated

measurements on the circuit so first of

all i prepared this set of measurements

to measure the efficiency and we can

look at that in the error log

so we can see that for this

configuration

we're getting about 28.6

so it's not great but it's more than 25.

now i also prepared this other set of

measurements

so this is to measure the voltage gain

of the circuit

by measuring the ratio between output

and input peak to peak voltages

and again this is present in the error

log and we're getting a value of about

13.

so it's less than the 15 that we would

be getting just based on the resistors

because we also have an equivalent

resistance in the emitter of the

transistor

finally we can look at the output signal

in an fft spectrum to see just how clean

it is

and we can see that we are getting some

extra harmonics

but the difference between the first two

peaks is around 34

35 decibels so we can call it decently

clean

now other than the transient simulation

we can also perform an ac simulation

so just to quickly see the bandwidth of

the circuit and if we look at the output

we can see we are getting a fairly flat

response

starting from around 10 kilohertz up to

around 10 megahertz so over three

decades of frequency

so this will be quite a decent wide

bandwidth amplifier

so now that we've seen that it works in

the simulator it's time to test it out

in real life

now without going into too many details

this is a really simple design after all

here is the finished circuit it's quite

compact and other than the large

heatsink for the power transistor and

the large inductor most components are

quite small

i did however use through-hole

components for the resistors to better

dissipate the heat but everything else

is surface mounted

also other than the components already

discussed

the circuit has a set of supply

decoupling capacitors and filters to

reduce any noise that would be otherwise

going out onto the supply lines

and that being said it's time to test

things out

so here is the first set of that i've

prepared

i've got my circuit is being supplied

from my power supply back here and i'm

passing the current through an ammeter

to get a more precise current

measurement

my signal generator will be providing

the signal into the circuit and the

output is connected to the

oscilloscope's first channel where i

have my 50 ohm termination resistor

so

first thing to check out

is the current consumption of the

circuit so this should be our very first

indicator to see whether the circuit is

working as expected or not so when i

connect

the power supply

you are getting about 139 point

something milliamps

and we can see that this current is

increasing

so as the transistor is warming up we

are getting more and more current

consumption

so this is very close to the total

current consumption that the simulator

was telling us about

now at the moment there is no output

signal we can see it's flat and if we

turn on the signal generator

so we're at 140 546 milliamps

with an output signal

not much has really changed so we are

still in the same region we see that

current is slowly decreasing

so again as some of the power gets

delivered transistor is getting slightly

colder so we have a small shift in the

current consumption

now if we look at the actual signal we

can see

we are getting a pretty nice sine wave

we can play around with the amplitude a

bit so if we increase the amplitude we

can see a bit of distortion occurring on

the bottom side also on the top side so

if the signal is small enough then it's

nice and symmetrical but if you increase

it too much then you start to get some

problems so we leave it like this

so at the moment we're getting 4.67

volts rms onto the 50 ohm load and this

is giving us a power of

436 milliwatts

now the first observation to make about

this is that if you want to make an

amplifier for half watt

design it for a bit more

otherwise you might run into distortions

and other problems

now anyway the current signal that we

are looking at is running at two

megahertz

so the other thing that we can play

around is the input signal frequency

so we can go up to three four five it's

starting to decrease so as frequency

increases

we start to get a smaller signal so this

is at five megahertz but we can also go

the other way

so one megahertz

let's just zoom in a bit more

for 400 kilohertz 200 100

we can see that we are still getting

roughly the same amplitude and we can go

even lower

so maybe you can already hear it it's at

10 kilohertz right now and even lower

and now the amplitude drops a lot more

so you can see that we are getting a

very wide bandwidth

but the best way to test it is not like

this

but rather with the body analysis so for

this measurement

i'm using a signal amplitude of about

900 millivolts and i'm running a sweep

between three kilohertz and 50 megahertz

just so you can see a nice and wide

response

and if we look at the measurement

so we have 10 points per decade we can

see we are getting a very nice very flat

response

all the way up to almost 20 megahertz so

between this 10 kilohertz point we're

getting an amplitude of 22 decibels

it stays relatively flat 22 22 22

all the way

up to 15.85

megahertz

and then it slowly drops off so it did

manage to make a very nice very wide

band amplifier

next we can look at modulation

performance so i left and yellow the

input signal in blue the output i'm

running at 500 kilohertz and the 500

millivolt input signal so there's no

point in checking out frequency

modulation we already saw that the

circuit has a very wide bandwidth so

let's look at some other types of

modulation first off being amplitude

modulation

so we can see that the input signal and

the output signal are almost identical

in shape maybe there's a bit of

distortion here on the bottom of the

blue signal

but that of course can be

adjusted by the input signal amplitude

otherwise the two signals are quite

identical

next we can try out phase modulation

so this is the type of modulation in

which the phase of the signal suddenly

changes

and we can see it on the input signal so

we've went from one phase to

completely different phase frequency

stayed the same but we had a very sudden

change

and we can see the same thing on the

output so the output is inverted but we

can see that the output signal very

closely followed the input signal so

there was no lag or nothing

the output followed the input exactly

final thing to look at is

ask type of modulation amplitude skip

keying and here again we can see that

the input signal and the output are very

well matched so there's no delay in the

output signal it's following the input

signal identically there's no variation

in amplitude it starts off

directly at full amplitude and then

turns off right as the input signal

disappears

so we are getting an all-around good

performance with any sort of signal

modulation

now final thing to do is test thermal

performance

so right now there is a signal passing

through the circuit

and i'm measuring the temperature on the

transistor on the screw that's holding

the transistor in place with a

thermocouple so which are getting about

51 52 degrees celsius we can also look

at the circuit with the thermal camera

so we can see the main

hot element is the transistor and the

heatsink but there's also a couple of

resistors in there which are also

heating up so when designing such an

amplifier it's also important to take

into consideration that

you're dissipating power not just on the

main amplifying element so you need to

take care with also the other components

now we can also look at what happens

with the amplifier if we turn off the

signal

so right now the signal is off

current consumption

stayed roughly the same

but since there's no more power being

delivered to the load we should be

seeing an increase in temperature since

now all of the consumed power

is dissipated on the transistor so as

with any thermal behavior

it takes the time it takes

but we can see that the temperature is

now slowly increasing

so we're at about 54 degrees and it will

probably increase a bit more

now the circuit works it's performing as

expected

but there are some interesting things to

point out regarding what could have been

done differently

specifically regarding the efficiency so

the main non-ideal elements which are

pushing us away from the

maximum theoretical efficiency

are the minimum collector emitter

voltage

not being zero but rather a couple of

volts

and also the voltage drop on the emitter

resistor

now you can use better transistors and

these voltages will drop slightly

but the fact remains that you will still

have 2-3 volts out of the supply voltage

being lost because of these non-ideal

behaviors and the need for feedback

now if you lose 3 volts out of 10 volts

it's a 30 percent loss but if you lose 3

volts out of say a hundred it's only

three percent

what i'm trying to say is that these

voltages are relatively fixed and

independent of the supply voltage

so as long as the correct impedance

matching is used on the output side you

can greatly improve efficiency

simply by using higher supply voltages

in the end the class a amplifier

provides the benefit of high linearity

which is highly priced in audio

applications and also allows the

possibility to amplify any sort of

modulation specifically useful when

talking about radio frequency signals

but it also has the important benefit of

simplicity

it can be built around a single

amplifying element

if the efficiency is not of big concern

this type of amplifier is extremely

useful and important and has a multitude

of applications

now if only there was a way to do

something about that efficiency

what's the next letter after a

anyway that will be it for today

so hope you got some instant information

to this leave your thoughts in the

comments thank you for watching make

sure to subscribe to be up to date at

tomatoes videos and see you next time

bye bye

you