Tip - OP Amp Configerations

What happens if the voltage source you want to sample is over 5V? Or you want to produce an analogue output between 0 and 24V? The answer is use an op-amp. A popular op-amp is the LM324, it has 4 amps on board, and only requires 1 power supply (most need 2 - a positive and a negative).

One thing to look out for is that an op-amp with a 5V power supply wont actually be able to swing to 5V, it will get to just over 4. If you want to have a voltage output swing of 0-5V, use a power supply 6V+, or a 0-12V swing, use a 13V+ power supply, any range up to 32V is possible.

Non-inverting amplifiers allow the output to be greater than the input by the value of gain. The values of the resistance are anything between 100K and 900K, if on ISIS, 1M resistors are used, it will assume its an open circuit, and the op-amp will not work correctly.. although this wont happen in real life.

Inverting amplifiers are used to sample negative voltages (or positive), and reverse the polarity while increasing / decreasing the output voltage depending on the gain. The gain can be calculated in the following examples:

Non-inverting Amplifier ( Video SIM of a Non-inverting Amp )

For an ideal op-amp, the non-inverting amplifier gain (Vout / Vin) is given by

Inverting Amplifier ( Video SIM of an Inverting Amp )

For an ideal op-amp, the inverting amplifier gain (Vout / Vin) is given simply by

For equal resistors, it has a gain of -1, and is used in digital circuits as an inverting buffer.

Buffer Amplifier ( Video SIM of a Buffer Amp )

Op-amps have a huge input impedance, and this feature is great to use to sample circuits with practically no additional load placed on it. A buffer amp is a great tool to use for applications like this.

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