# Designing Schematics for inverting 741 OPAMP

Discussion in 'Electronics Homework Help' started by citro250, Jan 21, 2014.

1. ### citro250

1
0
Jan 21, 2014
doing a little home project here for an opamp my cousin tells me I can make one with these components but I need to design the schematics, he tells me I can't do it but I think you can!
help me out!

Single ended supply
Power supply 9V dc at 10mA
Output impedance: 1kΩ
Input impedance: 2.2kΩ
Adjustable output level: max 40dB variable resistor, potentiometer
Frequency range: 20Hz to 20kHz +/-3dB
Max input signal 40mV
Max amplifier gain = 100

It is to use a 741 op-amp in the inverting mode on a single power supply built on Vero- board

Components given, parts list:
Resistors:
2.2kΩ
22kΩ ×2
220kΩ
RV1 1kΩ
Capacitors:
1µF ×2
10µF
IC
741 OP-AMP

2. ### Harald KappModeratorModerator

11,160
2,548
Nov 17, 2011
Here are single supply opamp circuits you can use with the 741.

By the way I do think your cousin is really your teacher and this belongs in the homework section.

3. ### BobK

7,682
1,688
Jan 5, 2010
The GBP of a 741 is 1MHz, so the gain at 20KHz will be 50, not meeting your spec. Also the 741 is a very bad choice for single supply operation.

Bob

4. ### Harald KappModeratorModerator

11,160
2,548
Nov 17, 2011
Bob is right, the 741 is quite a bit outdated and doesn't meet the specs.

But: -3dB at 20kHz is equivalent to a gain of 0.707 (compared to 0dB, where gain=1). Therefore max. gain of the opamp circuit in the passband (f <<20kHz) can be up to 70 (50/0.707) - still not the 100 required.
You can design the circuit for a max. gain of 100, but then the attenuation at 20kHz will be -6dB which is a violation of another requirement.

5. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,480
2,828
Jan 21, 2010
Well, it does specify the maximum gain.

Designing an amplifier with a lower gain still meets the spec <evil grin>