[sdiy] Expo converter tempco placement

[Justin Owen]

Hello,

Can anyone give any insight into the differences between the two main locations for tempco placement in expo converter circuits? 

Seems like the schems I have are divided fairly evenly between those who use a tempco (generally 2K) in the feedback loop of the CV scaling op amp that feeds into the base of the expo pair and those that use a tempco (generally 1K) as part of a voltage divider at the output of the CV scaling op amp.

Secondly, if you were using a tempco int he feedback loop of the CV scaling op amp - would there be any problems using that tempco in parallel or series with another standard R to achieve a certain R value?

Thoughts?

Thanks!

- Justin