# LM358N/TL082/741 Op Amps 5 Gain Circuits and 741 Op Amp Tester Circuit

lm358n 5 gain cct: 30V DC (max V = < 33V!), gain of 5 circuit Rf = 100k (pins 2 to 1); Rin (pin2),2Vpp sine input , inverting)= 20k; voltage divider 2 x 10k for 15V at pin3 (non inverting); clipping starts at 27.5Vpp for a 5.4Vpp input. This circuit swings quite close to within 2.5Vpp to rail voltage of 30V. Gain = 27.4÷5.36 = 5.11  Use the same cct as the dual amp lm358 for the dual tl082 as pinouts are same, so exact same gain results as lm358:  The 5 gain circuit only needs minor changes but at only 20V max PSU , not 30V!! (pins 8-7; 1-6) to use the 741 single amp package for same results for gain, as you would expect. The real FR of op amps is into the 100kHz ranges, not my 17kHZ phone out limits:   Note diagram pin 7 error of 30V – should be 20V: With the addition of the 0.01uF feedback cap from w2aew’s circuit: from output pin 6 to inverting input 2 of the 5 gain circuit you can see the same linear dis/charging of the cap if a square wave is input. Note how it bypasses the 5 gain 100k back to unity gain : Op Amp tester circuit:

https://circuitdigest.com/electronic-circuits/opamp-lm741-tester-circuit ￼￼￼“We just need to place the op-amp LM741 on right place and if the Op-amp is in good condition then LED will flash or Blinks, and if Op-amp is faulty then either LED will remain ON or OFF continuously.

Working of the circuit is simple, basically this circuit generates a Square wave at the output if op-amp is in working condition, resulting a Blinking LED. When we ON the circuit with op-amp is in place, initially voltage at non-inverting input (+) is higher than the voltage at inverting input (-) and output of op-amp LM741 (PIN 6) is High. So capacitor C1 starts charging through the resistor R6, when C1 charging exceeds the voltage at inverting terminal (PIN 2), then output becomes low. And when the output goes Low, capacitor C1 starts discharging and again voltage at inverting terminal of comparator becomes lower than non-inverting terminal and output goes High. This process repeats continuously and produces Square Wave at the output, which causes LED to Blink.

So if the Op-amp is in working condition, then LED will blink continuously at regular interval and if op-amp is faulty then LED will either stays ON or OFF.

This process of charging and discharging of capacitor is much similar to 555 timer IC in Astable mode, which also produces square wave at the output.”

It’s useful so I built it on perf board: