Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Constant amplitude output circuit design?

Status
Not open for further replies.

pavjayt

Member
Hello,

How would I create a circuit that outputs the same amplitude regardless of the input amplitude? The input is a sine wave which varies from 0.4V to 10.6V in amplitude with 0V offset. I would like to create an output to be a constant amplitude sine wave at 5Vpp.

The input sine wave is generated by a scanner driver at 15.75KHz
I want to use this as an input to a comparator, specifically ADCMP600

thanks
 
Last edited:
What frequency? audio?
Maybe you should tell us what you want to do. What are you making?
 
Last edited:
AGC comes to mind, but there is some lag with them before they respond. Would that work?
 
AGC comes to mind, but there is some lag with them before they respond. Would that work?
Not a problem as long as the lag is constant. At the end I want to generate a TTL signal from that sine wave that has minimal jitter.

thanks
 
After the agc you could just add a gain of 5 amplifier out of the other half of the 558.
 
You have a signal that is a sign wave with an amplitude of 0.4 to 10.6 volts. Frequency is 15750.
You want a TTL signal as the output.
My guess is that you don't care how it works.

If the above is true I don't see why we need a AGC circuit.
 
You have a signal that is a sign wave with an amplitude of 0.4 to 10.6 volts. Frequency is 15750.
You want a TTL signal as the output.
My guess is that you don't care how it works.

If the above is true I don't see why we need a AGC circuit.
Sorry, not sure what you mean exactly. Would be nice if you can share your idea if its better and simple.

thanks
 
The comparator you like can work to -0.2V on the inputs. (I think)
Here is a circuit I am using on a product.
Input on right side.
R600 limits the current if the input is too large. In your case you might want to change to 2200 or more.
D600 protects the IC.
R602, R603 adds Hysteresis. My IC has some and I wanted more.
The (-) input set the "slice point" which you want to be 0 volts.

I don't have time to think whats wrong with this circuit right now.
I am using this where "slice" is 0.5 to 2.5 volts. Some voltage comparators will work to -0.4 volts on the inputs so having "slice" at 0V should be fine. (look for common mode input voltage range)

If the input is above 0V the output will be at 5V. If the input is below 0v the output will be 0V.

upload_2014-6-10_22-22-20.png
 
Just amplify the smallest signal with a simple transistor amp to the value you want and let the larger signals clip in the amp. Don't see a reason for the complexity of an AGC circuit if all you want is a digital output.
 
Thanks to all of you. I will start with Zapper's suggestion then ronsimpson's and then ronv's. Of all I am gonna stick with the one that has the most stable output.
 
You have a signal that is a sign wave with an amplitude of 0.4 to 10.6 volts. Frequency is 15750.
You want a TTL signal as the output.
My guess is that you don't care how it works.

If the above is true I don't see why we need a AGC circuit.

Ditto

Ramesh
 
The comparator you like can work to -0.2V on the inputs. (I think)
Here is a circuit I am using on a product.
Input on right side.
R600 limits the current if the input is too large. In your case you might want to change to 2200 or more.
D600 protects the IC.
R602, R603 adds Hysteresis. My IC has some and I wanted more.
The (-) input set the "slice point" which you want to be 0 volts.

I don't have time to think whats wrong with this circuit right now.
I am using this where "slice" is 0.5 to 2.5 volts. Some voltage comparators will work to -0.4 volts on the inputs so having "slice" at 0V should be fine. (look for common mode input voltage range)

If the input is above 0V the output will be at 5V. If the input is below 0v the output will be 0V.

View attachment 86800

I tried what you suggested and its working only when I use 3V as V+ for TLV & btw, the shutdown pin should be connected to GND rather than 5V for it to be active. The jitter in the output is not any better than the TTL output that comes out of my source sine wave driver. I am trying to get the jitter as low as possible. Maybe I should just keep using a PLL in my circuit and maybe better it.

Probably it might be better for another thread, but while we are here, currently I am using the TTL coming out of my driver as input and the output as reference to a 4046 IC and the results are not as better as I expect it to be. This time I would like to try using TTL signal as input and the sine wave as the reference to a 4046. Could that be done?

Here is the circuit that I am currently using, the input TTL is via C14 and the output is across Pin11&12.

Any suggestions to modify the same circuit to use TTL as input and Sine as reference?

I am following this guide (among others)
 

Attachments

  • PLL.jpg
    PLL.jpg
    209.4 KB · Views: 196
Last edited:
Like others above, I see no need for AGC. Simply apply massive gain to cause clipping, so that the sine becomes square. Or else use a zero-crossing detector.
 
Like others above, I see no need for AGC. Simply apply massive gain to cause clipping, so that the sine becomes square. Or else use a zero-crossing detector.
I haven't tried AGC yet, but a simple transistor amp where I saturate with gain is not that stable. I want the output to be of very very low jitter or no jitter. The above reply I had is using a comparator like Ron suggested.
 
Hello,

How would I create a circuit that outputs the same amplitude regardless of the input amplitude? The input is a sine wave which varies from 0.4V to 10.6V in amplitude with 0V offset. I would like to create an output to be a constant amplitude sine wave at 5Vpp.

The input sine wave is generated by a scanner driver at 15.75KHz
I want to use this as an input to a comparator, specifically ADCMP600

thanks

Can a Schmitt Trigger work in this case? [It will change the wave , from Sine to Square]
 
Hi,

The best you can do is probably to amplify a little bit with an op amp, then use a zero crossing detector.
You want little or no phase shift in the amplifier, and detect as close to zero as possible so you do not introduce a varying phase shift with amplitude.
 
I want the output to be of very very low jitter or no jitter.
Won't simply using a comparator, or non-clipping AGC, introduce an amplitude-dependent phase-shift as MrAl mentions?
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top