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What is the significance of input and output impedances in the design of an amplifier?
Input Impedance, ZIN or Input Resistance as it is often called, is an important parameter in the design of a transistor amplifier and as such allows amplifiers to be characterized according to their effective input and output impedances as well as their power and current ratings.
What is loading effect in multistage amplifier?
Loading effect can be defined as the effect on the source by the load impedance. Usually loading effect reduces the voltage level of a voltage source. Amplifier input impedance are calculate taking both the bias resistances (R1, R2) and the transistor input (i.e. base input resistance), βr’e.
How can we reduce loading effect in amplifier?
To reduce the loading effect, an instrument must possess:
- Zero input impedance.
- Unit input impedance.
- High input impedance.
- Low input impedance.
What is the load effect?
Load effect is a power supply specification (also known as load regulation) that describes how well the power supply can maintain its steady-state output setting when the load changes. For example, if the power supply is set to 10 V, the actual output may measure 9.999 V with no load (0 A).
Why are impedances important in a multi stage amplifier?
The input and output impedances of an amplifier are very important parameters that affect the overall gain in multi-stage amplifiers. AC Theory Module 7.2 describes how correct matching reduces signal loss between the output of one amplifier and the input of the next in multi stage amplifiers.
What happens if the input impedance of an amplifier is too low?
If it is too low, it can have an adverse loading effect on the previous stage and possibly affecting the frequency response and output signal level of that stage. But in most applications, common emitter and common collector amplifier circuits generally have high input impedances.
How does a 2 stage amplifier circuit work?
This 2 stage amplifier circuit comprises of two stages each of which perform amplification on the incoming audio signals and output finally obtained at the end of 2nd stage. A simple Microphone was used to feed input audio signals followed by a coupling capacitor C1 which removes any DC element from audio signal.
When to use a high impedance transistor in an amplifier?
Where very high impedance and low noise is required in an amplifier input, it is common to use a field effect transistor (FET) in an amplifier’s input stage. Very high input impedance is obtainable with JFETs as its gate is voltage, rather than current operated.