Contents
Why the input resistance of the amplifier should be high?
The answer is the high input impedance is good for the amplifier circuit to have a good amplification of the input signal other wise we get low voltage in, so low amplification.
What is the input resistance of voltage amplifier?
2.5 Dynamic Input and Output Resistances
| ideal amplifier type | input resistance | output resistance |
|---|---|---|
| voltage | infinite | zero |
| transconductance | infinite | infinite |
| current | zero | infinite |
| transresistance | zero | zero |
How can I improve my impedance?
1. Using resistors to increase the total speaker impedance load. As shown from my diagram above, if you’re planning on using a lower impedance speaker you can add resistors in series in order to bring up the total impedance that the stereo or amp sees.
Which technique is used to improve the input impedance?
If we have low input impedance we will get low amplification. Generally, BJT (Bipolar Junction Transistor) have low input impedance (typically 1 ohm to 50 kilo ohm). So for this, bootstrapping technique is used to increase the input impedance.
Why does a transistor have a low resistance?
The low resistance in input circuit, lets any small change in input signal to result in an appreciable change in the output. The emitter current caused by the input signal contributes the collector current, which when flows through the load resistor R L, results in a large voltage drop across it.
What does a transistor look like as an amplifier?
The below figure shows how a transistor looks like when connected as an amplifier. The low resistance in input circuit, lets any small change in input signal to result in an appreciable change in the output.
What is the input and output resistance of an amplifier?
Amplifier input and output loading for (a) voltage and (b) current amplifiers. Similarly, for the voltage divider at the output, formed by the nonzero amplifier output resistance and the load resistance, Av · vin = vout and is independent of RL when rout = 0.
How is input impedance reduced by adding a transistor?
That base must also load the signal, too. So that must be treated in parallel, as well. The input impedance must be reduced by adding the transistor, not increased. Imagine what you are suggesting as an alternative.