Table of Contents
What is the output impedance of BJT?
The ideal output impedance is zero; an amplifier with a low ouotput impedance can provide a larger output current without a significant reduction in the output voltage.
What is input and output impedance of BJT?
The input and output impedance of an amplifier is the ratio of voltage to current flowing in or out of these terminals. When a signal source and load are connected to an amplifier, the corresponding electrical properties of the amplifier circuit can be modelled as shown.
What is the output of a BJT?
The output characteristics of BJT can be divided into three areas – cut-off, saturation and active region. In the cut-off region both collector-base and emitter-base pn-junctions are reverse-biased – transistor is off.
How do you calculate output impedance?
Zsource = output impedance = source impedance = internal impedance. The output impedance of a device can simply be determined. We use a load resistance Rload, to load the signal source impedance Zsource….
| Open-circuit voltage V1 | volts |
|---|---|
| Loaded circuit voltage V2 | volts |
| ↓ | |
| Output Impedance Zsource | ohms |
What is the input impedance of a BJT?
Important Points
| FET | BJT |
|---|---|
| Voltage-controlled device: voltage between gate and source control the current through the device. | Current-controlled device: Base current control the amount of collector current |
| High input resistance | Low input impedance |
| Slower in switching | Faster in switching |
Is BJT current controlled device?
A BJT is a current controlled device because its output characteristics are determined by the input current.
How can we use a BJT as an amplifier?
A transistor acts as an amplifier by raising the strength of a weak signal. The DC bias voltage applied to the emitter base junction, makes it remain in forward biased condition. This forward bias is maintained regardless of the polarity of the signal.
How do you reduce output impedance?
using a low input offset rail to rail op amp to act as a buffer to lower the output impedance. 😉 At the most basic level an amplifier is more of something out than that something goes in, but depending on semantics, you can get the opposite if so desired.