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LM324 can work with single supply???

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hippoo

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lm324 single supply

56_1161622012.GIF


Hand Calculation:
Voutput = 101 ( Vinput_2 – Vinput_1 ) = 5 ( 0.5V – 0V ) = 2.5V


Vcc = 5V & Vss = 0V:

Simulation Result:
Voutput = 844.580mV

Practical / Lab Result:
Voutput = 0.73V


Vcc = 5V & Vss = -5V:

Simulation Result:
Voutput = 2.5042V

Practical / Lab Result:
Voutput = 2.58V


Question:
Manufacturers claimed that the LM324N can be used with only one single supply. However, the simulation and practical result proved that the circuit (with this instrumentation amplifier circuit configuration) cannot work with only one single supply.

Kindly give me your comments.

Thank you.


Regards,
hippoo
 

Jepeto

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instrumentation amplifier using lm324

Disconnect R4 from GND and connect the resistor pin to 2.5vdc as virtual ground
You need to add the same voltage to inputs
 

hippoo

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lm324 amplifier circuit

Hi hi Jepeto,

Refer to your diagram, I agree with you that we should add a virtual ground (for your case, you put in the virtual ground as VREF = 2.5Vdc). However, with this additional VREF, the circuit configuration actually spoiled the main purpose of the circuit to have only ONE single supply. Or you means that you could make use of the only supply to give you two values such as 5V & 2.5V (using voltage divider circuit of resistor configuration? This may cause the main supply of 5V to fluctuate if the loading is big enough, right?)

Your circuit may work with only if your op-amp V- terminal is connected to the VREF +ve terminal.

Thank you for the comments.

I’m glad to have your further comments.


Regards,

hippoo
 

Jepeto

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lm324 instrumentation amplifier

“Single supply” for amplifiers usually means that only positive supply voltage needed
But for applications like positive input and inverting amplifier you must use virtual ground that you can make using resistors for voltage divider

“Single supply” for amplifiers usually means that only positive supply voltage needed
But for applications like positive input and inverting amplifier you must use virtual ground that you can make using resistors for voltage divider

The circuit above works with AMP –V connected to GND, only R4 (in yours circuit) and the inputs connected to VRFE
 

10kangstroms

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how lm324 works

You need to consider the voltages on the internal nodes of your inamp. Look at the annotated schematic below. No single-supply op amp can output a negative voltage when the negative rail is grounded.
 

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