Auto Attenuator design

Thread Starter

second_ed

Joined Dec 5, 2011
2
I need to design a auto attenuator. I will appreciate any tips, here are details/requirements

a previously designed system can take a maximum voltage of 10V rms. signal going in to the system can go beyond 10 V at certain points. So this attenuator has to attenuate the signal, independent of frequency,without distortion, when ever the signal is over 10 v.
 

tommydyhr

Joined Feb 3, 2009
39
This very well explained circuit should most likely suit your needs: http://sound.westhost.com/project53.htm . It's designed to be inserted in line with your audio signal. It delivers very low distortion levels, with it's use of a LDR as it's gain control element.

Edit: I may have misunderstood the topic. This circuit serves to limit the output of an audio amplifier by compressing the signal.
 
Last edited:

crutschow

Joined Mar 14, 2008
25,133
You need an AGC (Automatic Gain Control) circuit. A low distortion AGC can be built using an analog multiplier. Google "AGC Circuit" and you will get many hits.
 

Thread Starter

second_ed

Joined Dec 5, 2011
2
crutschow:I tried using AGC; but I do not want to amplify the low voltages; just attenuate whenever the signal in to the system is too high;
tommydyhr: I looked at the circuit suggested; it sounds promising but need to do little more research for parts and such;

thanks
 

joeyd999

Joined Jun 6, 2011
4,410
So this attenuator has to attenuate the signal, independent of frequency,without distortion, when ever the signal is over 10 v.
Ummm...the act of dynamically attenuating the signal is non-linear through time. Therefore, distortion *will* be introduced! The faster the rate-of-change of attenuation, the more distortion. Not sure if this is important, just thought I'd point it out...
 

crutschow

Joined Mar 14, 2008
25,133
crutschow:I tried using AGC; but I do not want to amplify the low voltages; just attenuate whenever the signal in to the system is too high;
Then you put a threshold on the AGC control voltage so that is provides no control (constant gain of 1) until the input voltage nears 10V. That could be done with a comparator on the input to detect when the reaches 10V. When it reaches 10V then you turn on the AGC control. The trick is to get a smooth transition from below 10V to above 10V input.
 
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