Why Opamp has high impedance and low output impedance?
Op amps need high input impedance because they are voltage-gain devices. In order for voltage to drop across the input, the impedance has to be very high, as ohm’s law states, V=IR. It’s also important to prevent the loading effect. If the impedance were small, the current draw would be high.
What is the input impedance and output impedance of op amp and why?
The input impedance of the op-amp looks like the load impedance to whatever is proving the signal to the op-amp. The output impedance of the op-amp looks like the source impedance to whatever is receiving the signal from the op-amp.
Do op amps have output impedance?
The output impedance of an ideal op amp is 0. This means that regardless of the amount of current drawn by an external load, the output voltage of the op amp remains unaffected. The ideal output voltage is divided between this internal resistance and any external load resistance.
Why is input impedance of op amp infinite?
The zero voltage between two input terminals means that if one input terminal is connected to a hard voltage source like ground, the other input terminal will also be at the same potential. In addition, since the current flowing into the input terminal is zero, the input impedance of the op amp is infinite.
What does the output impedance of an op amp look like?
The output impedance of the op-amp looks like the source impedance to whatever is receiving the signal from the op-amp. A source driving a load with a relatively low load impedance is said to be heavily loaded, and a voltage signal will require a high current.
How is output impedance affected by load changes?
Of course, this all depends on the changes in load current being slow enough for the op-amp and feedback network to keep up with. That means you can only count on this improvement in output impedance for load changes with frequencies in the operating bandwidth of your circuit (op-amp and feedback network).
Which is an external factor for op amp drive capability?
External factors for the op amp drive capability include output voltage headroom, i.e. the voltage difference relative to supply rails; input overdrive; total supply voltage; dc- vs. ac-coupled load; and junction temperature. It is obviously necessary to be able to specify the drive capability.
Why is the impedance of an amplifier so high?
Thus, as it’s high impedance, it acts as a small load. The high impedance ensures that it draws very little current. It is the amplifier’s task to convert a low energy, voltage-driven signal into a higher-voltage output signal.