The project basically provide gain any multiplier using op amp and mosfet part make the project adjustable gain using noninverting formula This is the project i have finished . Anyone else have an idea for design same specifiaction ?

 

View attachment 273945

The project basically provide gain any multiplier using op amp and mosfet part make the project adjustable gain using noninverting formula This is the project i have finished . Anyone else have an idea for design same specifiaction ?

i mean i used opamp for amplifying sine wave . can you give any advice other component instead of mine providing same function

 

We cannot give you answers like that but we can discuss your ideas. What is another way to get the same kind of function?

 

same specification ?

What exactly is the specification? Voltage/current/frequency/price limits/ranges ?

 

Sorry, I expressed myself wrong. I mean, do you have an alternative suggestion that meets the same function in this project?
For example, in this circuit, "I amplified the ac with opamp, could it be amplified with bjt or something else, or I used nmos to make the gain selectable, for example, what could be used instead of nmos". I would like to know if you have any suggestions for this circuit.

 

"... that meets the same function in this project?"

Well now, that is the whole point: What is the required function of this circuit? Novel circuit designs do not explain themselves; especially if the circuit has been designed poorly or wrongly. Does anyone here actually know just what this circuit is supposed to do?

 

View attachment 273945

The project basically provide gain any multiplier using op amp and mosfet part make the project adjustable gain using noninverting formula This is the project i have finished . Anyone else have an idea for design same specifiaction ?

Hello there,

It looks like there could be some problems with this circuit.

First, what is the zener for and why is it on the output of an op amp?

Second, do the mosfets work with a negative voltage as well as a positive voltage? The input sine goes plus and minus doesnt it? That means the mosfets drains go plus and minus referenced to ground. Can you find a way to fix that?

 

"... that meets the same function in this project?"

Well now, that is the whole point: What is the required function of this circuit? Novel circuit designs do not explain themselves; especially if the circuit has been designed poorly or wrongly. Does anyone here actually know just what this circuit is supposed to do?

It's an attempt to create an amplifier that has external variable gain control.

 

Second, do the mosfets work with a negative voltage as well as a positive voltage? The input sine goes plus and minus doesnt it? That means the mosfets drains go plus and minus referenced to ground. Can you find a way to fix that?

That doesn’t matter provided that the voltage on the MOSFET doesn’t go lower than -0.5V (i.e. the body diode doesn’t start to conduct)

But I would suggest a digitally controlled potentiometer, of which there are hundreds available, with all sorts of different control systems, SPI, I2C, up/down buttons etc.

 

Hello there,

It looks like there could be some problems with this circuit.

First, what is the zener for and why is it on the output of an op amp?

Second, do the mosfets work with a negative voltage as well as a positive voltage? The input sine goes plus and minus doesnt it? That means the mosfets drains go plus and minus referenced to ground. Can you find a way to fix that?

Sir i'm explaining , if i 'm wrong ,i already give dc offset, drain part of mosfet is not exposed to negative alternance.For zener diode
Let's say I increased the input signal to 100 mv with100 mv dc offset ,will be taken at the last 20 times, 2 v came, then 3 times output 6 came 3.3v zener will keep it constant as 3.3 for the controller.

 

It's an attempt to create an amplifier that has external variable gain control.

right !

 

Sir i'm explaining , if i 'm wrong ,i already give dc offset, drain part of mosfet is not exposed to negative alternance.For zener diode
Let's say I increased the input signal to 100 mv with100 mv dc offset ,will be taken at the last 20 times, 2 v came, then 3 times output 6 came 3.3v zener will keep it constant as 3.3 for the controller.

unfortunately i didn't find 3.3v zener i used 4.7v in simulation

 

Please post your .asc sim file.
Can you confirm the aim of this project is to amplify a small amplitude AC input signal, using a controllable-gain amplifier, to provide a signal limited to 0V to +3,3V suitable for input to a microcontroller?
How much signal distortion (apart from a DC offset) can be tolerated?
Does the amplifier gain factor need to be known accurately?

 

OK. So there is a single-sided supply voltage; the most negative the OPA316 output can be is zero volts. But the "+" input is driven by a sine wave which is negative every half cycle. Can the OPA316 output a 2X negative voltage to match the negative voltage at the "+" input?

 

Please post your .asc sim file.
Can you confirm the aim of this project is to amplify a small amplitude AC input signal, using a controllable-gain amplifier, to provide a signal limited to 0V to +3,3V suitable for input to a microcontroller?
How much signal distortion (apart from a DC offset) can be tolerated?
Does the amplifier gain factor need to be known accurately?

yeah i confirmed.The signal is 1 khz . Gain factor is given before the project my mentor said "i want to see the signal is amplified by 2 ,selectible,and 3 times. he said "do somehow you do"

 

ANYONE ELSE have a suggestion?

 

I am not entitled to suggest other than this: tell exactly what you had in mind to design the original circuit (you did?). Get it running properly and then post again. I smell you are trying to get opinions about the first.

 

That doesn’t matter provided that the voltage on the MOSFET doesn’t go lower than -0.5V (i.e. the body diode doesn’t start to conduct)

But I would suggest a digitally controlled potentiometer, of which there are hundreds available, with all sorts of different control systems, SPI, I2C, up/down buttons etc.

Hi,

Take a look at the source that is connected to ground, and the drain which can go plus and minus whatever the op amp puts out.

 

ANYONE ELSE have a suggestion?

Hi,

Yes, one thing that looks wrong is that the first op amp has a unipolar supply voltage yet the input is a bipolar sine wave.
That cant work right at all if you want undistorted output.

Rethink that part and see what you can come up with.

 

The circuit should work find for positive inputs only.