Why a voltage amplifier has high input resistance and low output resistance?

Now, if you are talking about a single NPN transistor as an amplifier.. the Base of the transistor is driven by current and can have a low impedance. The output has a high resistance because it wants a low current pullup resistor (IE: highest value resistor) to change the base current gain to the highest voltage gain.

Why is low output impedance needed?

Low output impedance is desired to suck the maximum current from the circuit. High impedance means the circuit draws or gives little power to the signal. low impedance means the circuit draws or gives more power to the signal.

What is the output resistance of an ideal amplifier?

Basic Concepts of the Integrated Operational Amplifier 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.

Why Opamp has high impedance and low output impedance?

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. Low impedance circuits can be dangerous because of the high current draw that they produce. Op amps avoid this by having very high input impedance.

Which amplifier has lowest efficiency?

Class A amplifier
Accordingly, the Class A amplifier provides a linear output with the lowest distortion, but it also has the lowest efficiency level.

Why the efficiency of Class A amplifier is low?

Since the transistors in Class A amplifier, are forward biased all the time, few current will flow through them even though there is no input signal and this is the main reason for its poor efficiency. Generally, the current flows through the collector resistive load, this will cause the wastage of the DC power in it.

When negative voltage feedback is applied to an amplifier the voltage gain?

The following points are worth noting : (i) When negative voltage feedback is applied, the gain of the amplifier is reduced. Thus, the gain of above amplifier without feedback is 10,000 whereas with negative feedback, it is only 100.

Why is the output impedance of one amplifier lower than the other?

If a voltage transfer is to be realized, the output impedance of the first amplifier should be much lower than the input impedance of the next amplifier. This maximizes, such as what we described for the input stage, the voltage drop across the input impedance of the second amplifier rather than in the output impedance of the first.

How does resistance affect voltage drop across an op amp?

So the greater the resistance (or impedance) of a device, the greater the voltage drop across that device is. To make sure that the voltage signal drops fully on the op amp, it must have a very high input impedance, so that the voltage drops fully across it.

How do you increase the efficiency of a voltage amplifier?

Generally, a high efficiency is preferred for voltage amplifiers. It can be achieved by setting the input impedance of the stage n+1 much higher than the output impedance of the stage n.

What is the difference between voltage and current amplification?

For voltage amplification you want low output impedance from the previous stage and high input impedance from the next stage to maximize the voltage gain. For current amplification you want the reverse: high output impedance from the previous stage and low input impedance from the next stage.