Receiver circuitry comparisons

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metermannd

Joined Oct 25, 2020
202
When I posted my previous thread asking about eliminating the use of a second power supply from a board I was looking at reproducing, another regular had expressed puzzlement over the design of the actual receiver stage, so I thought I'd post four variations that I knew of for comparison's sake.

The oldest of the four designs is the "Two", the "3000" was a fairly long-lived version, the "3100" is a newer version due to the lower Vcc on the newer processor. The "901" design seems to be for working with particularly weak signals (no, I don't know why all those diodes; yes, it's practically overkill compared to the others).

It's interesting to note these four styles feature a bridge rectifier just before the tank stage(s), and all use the same method in transforming the amplified sine wave into a square wave before sending it on to the logic section.

The frequency of the signal for all is 12.5kHz, and the minimum expected amplitude of the incoming signal was 5mV p-p (1.5mV for the '901').

Also, note the "Two" circuit is the only one using a zener to derive the 2.5V supply, while the others all depend on a simple voltage divider (hence my prior question).

I'm mulling over the possibility of using the "3000" receiver stage instead of the "Two" stage, just to get away from using the near-obsolete CA3140 (3x as expensive as the TLC272!), while keeping the 2.5V zener supply.
 

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Audioguru again

Joined Oct 21, 2019
3,319
A modern TLC272 dual opamp that works with a supply as low as 3V is completely different to a cheap old TL082 that barely works when its supply is "only" 7V.
 
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