# Design an amplifier circuit

Discussion in 'Homework Help' started by Chaos-Mayhem, Jan 8, 2011.

1. ### Chaos-Mayhem Thread Starter New Member

Jan 8, 2011
2
0
I need help on this one, I'm trying to design an amplifier circuit with the following voltage gain: Av = -2. The input voltage will be 5 sin (2∏1000t).
I understand that Av = -(Rf/Ri) but not clear about the input voltage and how it relates to the design. Any help would be greatly appreciated.

Last edited: Jan 8, 2011
2. ### steinar96 Active Member

Apr 18, 2009
239
4
Since you mention Rf and Ri i assume it's a op-amp amplifier. In that case knowing the input signal helps choosing the proper opamp since op-amps have different slew rates for example(how fast they can track the rate of change of signals). And ofcourse you have to provide a power supply with a higher voltage then the maximum input signal swing multiplied with the gain of the op amp.

3. ### cigarsnob New Member

Feb 23, 2010
7
1
Following the previous post...the negative supply rail of the op amp must be greater than -10 volts. Best to go with -15 volts for the neg. supply rail. Also, since you know the voltage gain required (Av=-2) and since you know the gain equation, just choose an Rf and Rin value to achieve your gain. Remember to pick an appropriate Rin size (greater than 1k). Finally, looking at the BW of the amplifier helps, but since your signal is only 1kHz, I wouldn't really bother with that but foot to know for future use.

4. ### Chaos-Mayhem Thread Starter New Member

Jan 8, 2011
2
0
Thanks for your help that put me on the right track.