testing LM324 OP-AMP

[hussamaldean]

Hi,
I want to build PWM generator circuit using this op-amp. however, I start to doubt that the op-amp is not working since it doesn't draw any current from my PSU
is there any way to test if it does work ?
Regards

[Brutte]

If it does not draw any current (i<1pA) then there is no need to investigate that part further.
Idling device should draw idle current, more or less.

[precaud]

: Double-check your supply voltages.
: Short pin 1 to pin 2
: Put a 1kHz signal into pin 3
: Measure at pin 1, should be the same as the input at pin 3.

[hussamaldean]

: Double-check your supply voltages.
: Short pin 1 to pin 2
: Put a 1kHz signal into pin 3
: Measure at pin 1, should be the same as the input at pin 3.

I'll test it soon

If it does not draw any current (i<1pA) then there is no need to investigate that part further.
Idling device should draw idle current, more or less.

I can't be 100% sure since my psu has 10mA resolution only (Uni-t UTP3315TFL)
so basically I can't be 100% sure

[Zero999]

Post the schematic.

The LM324 seems to be a poor choice for a PWM circuit, because it's very slow.

[hussamaldean]

Post the schematic.

The LM324 seems to be a poor choice for a PWM circuit, because it's very slow.

[Zero999]

Post the schematic.

The LM324 seems to be a poor choice for a PWM circuit, because it's very slow.

The LM324 is no good for that circuit. Use a comparator IC with a push-pull output, such as the LMC6762 or TLC3702. Alternatively, the LM393 or LM339 will work with 1k pull-up resistors to 5V.

You'll need to make sure the MOSFET can pass the required current, with a gate voltage of 5V. Consider powering the PWM circuit off 9V, directly from 12V or using a MOSFET driver IC.

What's the maximum expected supply voltage? Will this be run off a car's electrical system? It may be necessary to add some overvoltage protection circuitry

[hussamaldean]

Post the schematic.

The LM324 seems to be a poor choice for a PWM circuit, because it's very slow.

The LM324 is no good for that circuit. Use a comparator IC with a push-pull output, such as the LMC6762 or TLC3702. Alternatively, the LM393 or LM339 will work with 1k pull-up resistors to 5V.

You'll need to make sure the MOSFET can pass the required current, with a gate voltage of 5V. Consider powering the PWM circuit off 9V, directly from 12V or using a MOSFET driver IC.

What's the maximum expected supply voltage? Will this be run off a car's electrical system? It may be necessary to add some overvoltage protection circuitry

the circuit for reference, I will use L298D motor driver though