I have finished project but i need alternative for my design

Thread Starter

d.akkas3

Joined Aug 3, 2022
12
Screenshot_1.png

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 ?
 

Thread Starter

d.akkas3

Joined Aug 3, 2022
12
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
 

Thread Starter

d.akkas3

Joined Aug 3, 2022
12
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.
 

RBR1317

Joined Nov 13, 2010
698
"... 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?
 

MrAl

Joined Jun 17, 2014
9,333
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?
 

MrAl

Joined Jun 17, 2014
9,333
"... 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.
 

Ian0

Joined Aug 7, 2020
5,819
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.
 

Thread Starter

d.akkas3

Joined Aug 3, 2022
12
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.
 

Thread Starter

d.akkas3

Joined Aug 3, 2022
12
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 :(Screenshot_2.pngScreenshot_3.png
 

Alec_t

Joined Sep 17, 2013
13,041
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?
 

RBR1317

Joined Nov 13, 2010
698
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?
 

Thread Starter

d.akkas3

Joined Aug 3, 2022
12
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" :(
 

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atferrari

Joined Jan 6, 2004
4,647
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.
 

MrAl

Joined Jun 17, 2014
9,333
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.
 

MrAl

Joined Jun 17, 2014
9,333
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.
 
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