programmable gain amplifier

[monishakumar]

programmable gain amplifier using instrumentation amplifier & logic state control using demux...

if any problem in my circuit design plz help....

my circuit design in proteus ...
pga simulation not work... what problem tell me....then how i go for correct design.....:???:

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this my ckt design plz find what problem

i design instrumentation amplifier with variable resister (Rg)
my gain varied 10 to 50 (10,20,30,40,50).so, each gain i find out Rg value
i use op07 for instrumentation amplifier
i use 4051(8 channel mux/demux) for demux
i use logic state for (000 condition to 111 condition)
i must be used logic control instrumentation gain
so i use demux ,when i given
input 000 condition d0 output only on , R1 resister only on,my gain 10
input 001 condition d1 output only on ,R2 resister only on,my gain 20
input 010 condition d2 output only on ,R3 resister only on,my gain 30
input 011 condition d3 output only on ,R4 resister only on,my gain 40
input 100 condition d4 output only on ,R5 resister only on,my gain 50
input 101 condition d5 output only on ,R6 resister only on,my gain 60
input 110 condition d6 output only on ,R7 resister only on,my gain 70
input 111 condition d7 output only on ,R8 resister only on,my gain 80
i simulated my design(programmable gain amplifier)
but i get result saturated output

 

[FvM]

There's no 4051 visible in the schematic. The shown schematic has 4002 nor gates with shorted outputs and can hardly work. I can imagine to use a 4051 analog multiplexer in a programmable gain amplifier, but I don't know if you did it right.

 

[monishakumar]

i am done programmable instrumentation gain amplifier......

 

[FvM]

The exact circuit gain will depend on the analog switch resistance, voltage dependent resistance will introduce nonlinearity. To avoid these problems, the multiplexer should be connected in a way that no signal currents flows through the switches.