communication ckts using OTAs

Thread Starter

Lubna

Joined May 5, 2013
7
I recently read in a journal that the compander and the adaptive delta modulator circuit could be implemented through OTAs. it was mentioned that the value of step size and µ ( they were using a µ law compander circuit) could be varied by varying the transconductance of the otas used. how are these parameters varied in conventional compander and delta modulator ckts? I want to know the advantage of using otas for these ckts.
 

MrChips

Joined Oct 2, 2009
30,618
I don't know what OTA means.

So I had to do a search.

OTA stands for Operational Transconductance Amplifier.

Now I know.
 

Thread Starter

Lubna

Joined May 5, 2013
7
sorry I did not elaborate upon OTA. it is a voltage controlled current source whose transconductance can be varied through an external bias current. it is a low power device so it can be used in micro power applications. I just want to know that how are the values of step size and
µ controlled in conventional delta modulator and compander circuits so that I can understand the purpose of using OTAs for implementing these ckts.
 

KL7AJ

Joined Nov 4, 2008
2,229
I recently read in a journal that the compander and the adaptive delta modulator circuit could be implemented through OTAs. it was mentioned that the value of step size and µ ( they were using a µ law compander circuit) could be varied by varying the transconductance of the otas used. how are these parameters varied in conventional compander and delta modulator ckts? I want to know the advantage of using otas for these ckts.
An OTA is ideal for doing this....though there are newer methods. By a simple DC control voltage, you can control the gain over a very wide range. The key to A law and U-law implementation is how you derive the FEEDBACK to control the DC voltage

A typical compressor would rectify a small sample of the output signal and apply this to the gain control of the OTA. The matching expander would use the same method, but with a simple polarity reversal of the feedback voltage.

Eric
 
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