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# Class a amplifier

#### wien

##### Newbie level 6
I'm trying to connect a class A power amplifier to a circuit that has a resonance frequency of 110 kHz, has 11 v, and has almost no current. I'm trying to make about 10w of power by using the amplifier to make 1A of current. Vcc is trying to use 15v or 12v. Vcc uses 12v or 15v and please recommend resistance values for that

Does it have to be Class A ?

Unless you make Rc a parallel resonant LC and remove Re you will find it hard to get 10W from that schematic and you would need a large heat sink on the transistor. Used in that configuration you probably also need an output coupling capacitor to block DC passing straight into the load.

I would suggest a Class B or AB push-pull output stage instead, it would be far more efficient for little extra complication.

Brian.

What specifically is your load Z ? Specs and a description, is it capacitive,
inductive ....?

Is this a school test ?

Regards, Dana.

Can A-level and A-level amplifiers be boosted to 10W?

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What specifically is your load Z ? Specs and a description, is it capacitive,
inductive ....?

Is this a school test ?

Regards, Dana.

Try to eliminate or minimize Re value.

Drive the transistor so its average resistance gravitates to a value about the same as your load.

This creates output centered at 1/2 supply V.

### wien

Points: 2
What specifically is your load Z ? Specs and a description, is it capacitive,
inductive ....?

Is this a school test ?

Regards, Dana.
It's not a school exam, it's a circuit used for machines that need to be made in projects that schools do. I'm a high school student, so I'm new to circuits this time, so I don't know much about them yet. There's no specific frame, so I just need to make 10w. I'm not sure, so can you tell me what load Z is?

Hi,

voltage, current, impedance.
You know Ohm´s law?

In my eyes it can´t work with
* 11W
* almost no current
* how do you think to "make" 1A
++++
What I don´t understand:
You talk about "a circuit that has a resonance frequency of 110 kHz, has 11 v, and has almost no current."
What is it?
Somehow I think about an RLC. But series, parallel?

So we know ther is a circuit with 11kHz resoanance. But is the electrical (amplified) signal also exactly the resonance frequency.
(To do so it needs to follow all tolerances and drifts "of the "mysterious cicuit"

You talk about "11V". What is it? 11V RMS, peak, peak-to-peak? Something else?
Same with "1A"

To me it´s all a riddle without any meaningful function / information / use..

Klaus

Rather than play with circuits with no chance of working as you expect ( 110 kHz 1A from a TL072 into a Class A ), let's review your specs & tolerances so you ask questions about what you need to learn.

10Vac Units? Vp, Vpp, Vrms, Vavg These are all relative to how it is measured and what you need.
Tolerance = roughly ? variable ? or just managed to get? It is better to say tuneable or fixed with say X% tolerance. such as X= 10% or can you imagine a need for 1% ?
Freq = 110 kHz sine, Was this by accident when you were trying to get something else.
Quality = Different attributes are used for sine, square, triangle, sawtooth, stair-case and all these can be synthesized in circuits. e.g. specify f = ___ +/- ___ sine ___% total harmonic distortion (THD) or for square wave, < 1% asymmetry, for sawtooth ___% linear error.(gain, offset or curve) max
Environment = ? Indoor (Benign), Consumer temp range, Industrial temp Range, Military temp and mechanical environment. (shock & vibe)
Load = ? define RLC values Ohms, Henries, Farads with tolerances, then current in Amps can be computed. DC motors for example draw > 10x the start current as rated current and all inductors have a DC resistance or DCR. All Capacitors have an equivalent series resistance, or ESR.
Thermodynamics= Power dissipation max, Temp rise max, implies a heat sink required with thermal resistance 'C/W.

This can be expanded or simplified. But the bottom line is to engineer something means to define is measurement qualities and limitations and all the quantity assumptions like power, voltage, temperature and impedance. For questions, it is good to state your limitations on tools, experience and preferences to learn for better answers. Like is this just for simulation fun, prototype or hobby or future profession.

This may seem boring, but engineering needs to be data-driven with specs and tolerances.

However , I can see a dozen things go wrong with this circuit, I made for you. For your amusement.

Maybe all you care about is finding a current amplifier that works better than Class A.
If you can read schematics, look at discrete audio power amps.

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KlausST and wien

### wien

Points: 2
It's not a school exam, it's a circuit used for machines that need to be made in projects that schools do. I'm a high school student, so I'm new to circuits this time, so I don't know much about them yet. There's no specific frame, so I just need to make 10w. I'm not sure, so can you tell me what load Z is?

The load Z is the impedance of the load, what the 10W is driving. Is it an ultrasonic
transducer, a motor, a speaker, a lamp, a led, what is the 10W amplifier used for
other than creating heat (its 10W will ultimately appear as heat in some form).

Regards, Dana.

안녕,

전압, 전류, 임피던스.
옴의 법칙을 아시나요?

내 눈에는 그게 효과가 없을 것 같아
* 11W
* 전류가 거의 없음
* 1A를 "만드는" 방법은 어떻게 생각하시나요?
++++
내가 이해하지 못하는 것:
"공진 주파수가 110kHz이고, 전압이 11V이며, 전류가 거의 없는 회로"에 대해 이야기하셨는데요.
그것은 무엇입니까?
어떻게든 RLC에 대해 생각해. 하지만 직렬, 병렬?

그래서 우리는 11kHz 공진을 가진 회로가 있다는 것을 압니다. 하지만 전기적(증폭된) 신호도 정확히 공진 주파수입니까?
(그렇게 하려면 "신비한 회로"의 모든 허용 오차와 편차를 따라야 합니다.

당신은 "11V"에 대해 이야기합니다. 그게 뭔데요? 11V RMS, 피크, 피크-투-피크? 다른 거요?
"1A"와 동일

저에겐 이 모든 것이 의미 있는 기능/정보/용도가 없는 수수께끼일 뿐입니다.

클라우스

예상대로 작동할 가능성이 없는 회로(TL072에서 클래스 A로 110kHz 1A)로 놀기보다는 사양과 허용 오차를 검토하여 알아야 할 사항에 대해 질문해 보겠습니다.

10Vac 단위 ? Vp, Vpp, Vrms, Vavg 이 모든 것은 측정 방법과 필요한 것에 따라 다릅니다.
허용 범위 = 대략? 가변적? 또는 그냥 얻을 수 있었나요? 조정 가능하거나 X% 허용 범위로 고정된 것이 더 좋습니다. 예를 들어 X= 10% 또는 1%가 필요할 수 있다고 상상할 수 있나요?
주파수 = 사인파 110kHz, 다른 것을 얻으려고 할 때 우연히 그런 결과가 나왔나요?
품질 = 사인파, 사각파, 삼각파, 톱니파, 계단형에 대해 서로 다른 속성이 사용되며 이러한 모든 속성은 회로에서 합성될 수 있습니다. 예를 들어 f = ___ +/- ___ 사인파 ___% 총 고조파 왜곡(THD) 또는 사각파의 경우 < 1% 비대칭, 톱니파의 경우 ___% 선형 오류(이득, 오프셋 또는 곡선) 최대값을 지정합니다.
환경 = ? 실내(양성), 소비자 온도 범위, 산업 온도 범위, 군사 온도 및 기계적 환경(충격 및 진동)
부하 = ? RLC 값 옴, 헨리, 패럿을 허용 오차와 함께 정의하면 전류(암페어)를 계산할 수 있습니다. 예를 들어 DC 모터는 정격 전류보다 10배 이상 시동 전류를 소모하고 모든 인덕터는 DC 저항 또는 DCR을 갖습니다. 모든 커패시터는 동등한 직렬 저항 또는 ESR을 갖습니다.
열역학 = 최대 전력 소모, 최대 온도 상승은 열 저항 'C/W'를 갖춘 방열판이 필요하다는 것을 의미합니다.

이것은 확장되거나 단순화될 수 있습니다. 하지만 결론은 무언가를 엔지니어링한다는 것은 측정 품질과 한계, 그리고 전력, 전압, 온도, 임피던스와 같은 모든 양적 가정을 정의하는 것을 의미합니다. 질문에 대한 경우, 더 나은 답변을 얻기 위해 도구, 경험 및 선호도에 대한 한계를 명시하는 것이 좋습니다. 이것이 시뮬레이션 재미, 프로토타입 또는 취미 또는 미래의 직업을 위한 것일 뿐입니다.

지루할 수도 있지만 엔지니어링은 사양과 허용 오차를 바탕으로 데이터를 기반으로 진행되어야 합니다.

하지만, 내가 당신을 위해 만든 이 회로에는 12가지의 잘못된 것이 보입니다. 당신의 즐거움을 위해서요.

View attachment 192206

아마도 여러분이 궁금해하는 건 클래스 A보다 더 잘 작동하는 전류 증폭기를 찾는 것뿐일 겁니다.
회로도를 읽을 수 있다면 개별 오디오 파워 앰프를 살펴보세요.
Thank you for always doing your best to answer questions. I learn a lot thanks to you.
--- Updated ---

부하 Z는 부하의 임피던스이며 10W가 구동하는 것입니다. 초음파입니까?
변환기, 모터, 스피커, 램프, LED, 10W 앰프는 무엇에 사용됩니까?
열을 생성하는 것 외에는(10W는 결국 어떤 형태로든 열로 나타날 것입니다).

안녕하세요, 다나.
I'm going to make a receiver for a magnetic resonance wireless transmitter circuit. So I used a Winbridge oscillator to make a circuit with a resonance frequency of 110 kHz and 11V at 110 kHz as shown in the picture above. But my goal is to transmit 10W, so I need 1A of current. The purpose of this circuit is to transmit power.

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The purpose is not clear.

Is this to transfer power or data or both? i.e WPT

What units? 1A rms? What about frequency tolerance?
Show a block diagram with signal parameters.

Do you already have a magneto resonant antenna pair?

If you have a high Q, then you can drive it with a square wave FET like a power supply.

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The purpose is not clear.

Is this to transfer power or data or both? i.e WPT
What units? 1A rms?
Show a block diagram with signal parameters.
Remember tolerance errors cause loss of power in high Q. This is why you must specify tolerance.

Do you already have a magneto resonant antenna pair?
It's only for transmitting power. It transmits in a resonant magnetic coupling method. I haven't made antenna pairs yet. My role in the project is to make a transmitter, so I don't know the antenna, but when I make a transmitter circuit, I decided to make the antenna accordingly.

OK but you said "I'm going to make a receiver" Rx what ? power or data?
If you research Wireless Power Transfer or WPT, you will find thousands of research articles on magneto resonant loop antennae with high-current film capacitors and transmitter-receivers. You might find one more useful by choosing keywords to add to the search.

The choice of configurations, power driver and antenna tuning is the tricky part.

If you hit a "paywall", often the title can be found on www.Researchgate.com , which is free.
e.g. transmit coils

OK but you said "
If you research Wireless Power Transfer or WPT, you will find thousands of research articles on magneto resonant loop antennae with high-current film capacitors and transmitter-receivers. You might find one more useful by choosing keywords to add to the search.

The choice of configurations, power driver and antenna tuning is the tricky part.

View attachment 192209

If you hit a "paywall", often the title www.Researchgate.com , which is free.
e.g. transmit coils
OK but you said "
If you research Wireless Power Transfer or WPT, you will find thousands of research articles on magneto resonant loop antennae with high-current film capacitors and transmitter-receivers. You might find one more useful by choosing keywords to add to the search.

The choice of configurations, power driver and antenna tuning is the tricky part.

View attachment 192209

If you hit a "paywall", often the title www.Researchgate.com , which is free.
e.g. transmit coils
I made a mistake. I make a transmitter.
--- Updated ---

This is an example of a transmitter made by someone else. This person also used an oscillator and then an amplifier.

I can guarantee that is not class A !
Why do you specify class A, for WPT there is no need for conduction over the full cycle or great linearity.
Incidentally, the schematic in post #15 seems to connect R4 wrongly, my guess is the top and wiper should not have a link across them. I'm not sure D1 is useful either.

Brian.

Also, the D1 is clearly reversed.
It ought to convert a bipolar sine to a unipolar positive biased sine wave with a diode -ve clamp.
The pot appears to bias ineffectively the peak gate voltage during conduction. However, the square law effect (Vgs-Vt)² adds distortion making the sine oscillator a poor choice in the 1st place when a square wave osc can be more accurate and efficient with a high Q series resonator.

Overall, not a great implementation but without specs, it doesn't matter.

Hi,

and R4... is connected as variable load.

this is another example why not to use random circuits from the internet. There is so much nonsense around.
As Tony already mentioned .. there are many really good solutions. Look for reliable sources like
* semiconductor manufacturers
* universities
* reputable engineers

these documents usually also give informations like
* theory of operation
* formulae
* part selection
* and so on.

Klaus