Transistors Circuits

Transistor

A small electronic device used in a circuit as an amplifier, switch and oscillator.

NPN Transistor

A transistor that has two N-type semiconductors and one P-type semiconductor bonded together

A base in a transistor does what?

Allows some current to pass between the emitter and the collector

Disadvantages of Direct coupling (3)

At high frequency amplification cannot be achieved,, efficiency is less (dc) power loss, Poor Q point stability

Disadvantages of Transformer coupling (3)

Bulky, Costly, More space, Frequency distortion high

common emitter circuit (4)

Emitter is common in both circuits, Mid range current and voltage gain, High power gain, Input signal is inverted for output

Advantages of Transformer coupling (4)

Excellent impedance matching, No loss of signal (DC) power, High gain

Disadvantages of RC coupling (3)

Not good for impedance matching, Not great gain ( Voltage, Power), High noise

Types of coupling in Multi stage Amplifier (3)

RC, Transformer, Direct

A emitter in a transistor does what?

Sends the output voltage

Advantages of Direct coupling (4)

Simple Circuit, low cost, Good Frequency, Good impedance matching

Advantages of RC coupling (4)

Simple, Cost effective, Less space & weight, used in AF range

PNP Transistor

Thin Piece of N-type between two P-Type Materials; negative voltage applied

Voltage Divider

Two resistors are used to divide voltage, Emitter is shared

Active mode (amplifier)

Vb is equal to 0.7, Ib is between 0 and mx current, Vc and Ve is between 0 and max voltage

In Saturation mode a transistor

acts like a short circuit. Current freely flows from collector to emitter

In Cut off mode a transistor

acts like an open circuit. No current flows from collector to emitter

A collector in a transistor does what?

collects electricity

Uses of a transistor

electronic switch, oscillators and amplifiers

Disadvantages of Self Bias

negative feedback, reduces gain of amplifier

Disadvantages of Fixed Bias

poor stabilization, strong chances of thermal runaway

As you add stages bandwidth will ____ and your gain will ______

reduce, increase

Advantages of self Bias

simple, High stability, gets its own voltage

Advantages of Fixed Bias

simple, less components, bias conditions are easily set

Transistors are biased by

supplying Base with a control amount of voltage and current in order for it to work

Transistor that is not properly bias

will not work properly