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input 5,0 V output 5,-5V

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firsttimedesigning

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I want to make a circuit that will produce 5V when the input is 5V and produce -5V whent he input is 0V. Does such circuit exist? I have tried several ways, but none of them worked. So if there is any suggestion, please post it. Thanks
 

Hi Firsttimedesigning,

Try this.

48_1184646034.gif


on1aag.
 
Thank you for the reply. The circuit works. I can see that when Vin is 0V, the circuit functions as an inverting amplifier. However, I dont get how does the circuit work when it's Vin is 5V. Please explain it to me, thank you. What I really dont get it, why is R/2 resistor necessary?
 

firsttimedesigning said:
Thank you for the reply. The circuit works. I can see that when Vin is 0V, the circuit functions as an inverting amplifier. However, I dont get how does the circuit work when it's Vin is 5V. Please explain it to me, thank you. What I really dont get it, why is R/2 resistor necessary?
Click to expand...

when Vin is 5V, theOPAMP's Vin- will be 5V,too.
so there is no current at R.
No current means the Vout must equal Vin-, so the output is 5V.
 

But, what is the necessity of R/2 value. Even without this resistor the output will be +5V (no output current in R), why specifically, R/2??
 

when Vin=5V then due to virtual ground the other input's voltage is also 5V and hence no current flows and hence the output voltage is 5V.

as for the R/2... it is to make the input impedance of both the inputs equal.... those two R in the other input can be considered as voltage dividers and hence their impedance is R/2.

Regards
Anand
 

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