How does the circuit works

user4090349

Intellectual 811 points

Hello

In szza030d, I found an application using mux to set the op amp gain. But I don't understand how it works.

Could you explain it in more details?

over 2 years ago

0 Ron Michallick over 2 years ago

TI__Guru*** 149206 points

Hello user,

In this circuit the gain polarity is changed.

With switch as drawn, positive input is ground so output = -1 * input, because both R currents and voltages are the same. Gain = -Ri/Rf = -1

With switch in other position, input is applied to both op amp inputs. So no current can flow though either R, the only linear solution is vout = vin. Gain = +1

0 user4090349 over 2 years ago in reply to Ron Michallick

Intellectual 811 points

Hello Ron

Thanks for your explanation. Is it possible to switch the gain with a multiplexer, for example, 1 gain/1.5 gains/8 gains

Thanks!

0 Ron Michallick over 2 years ago in reply to user4090349

TI__Guru*** 149206 points

Something like this.

Both switches open is gain 8. G1 closed is gain 1. Just G1.5 is 1.5 gain. 70k in parallel with 5.38k is 5k

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Switches & multiplexers

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How does the circuit works