It is done when you use common emitter configuration.

The common emitter voltage follows this change and goes down thus making Q1 conduct more.

As a result, the common emitter resistor R acts nearly as a current source.

The load line diagram at right is for a transistor connected in a common emitter circuit.

The heart of an I2L circuit is the common emitter open collector inverter.

Common emitters are also commonly used as low-noise amplifiers.

The output is buffered by a common emitter amplifier.

The most important parameter for transistors is usually the forward current gain, h, in the common emitter configuration.

Two cascaded common emitter stages are shown below.

Current gain in the common emitter circuit is obtained from the base and the collector circuit currents.

For example, a common base may be used as a current buffer at the output of a common emitter stage, forming a cascode.

All amplifier stages used common emitter amplifiers.

In this case, the common emitter voltage and Q1 collector voltage are not suitable for outputs.

'E' refers to the transistor operating in a common emitter (CE) configuration.

In the case of bipolar junction transistors, the three classes are common emitter, common base, and common collector.

As a result, the common emitter voltage and Q1 collector voltage follow the input voltage.

Electronically, this can be accomplished by using a simple high pass filter, realized by an RC circuit, in front of a common emitter amplifier.

In the forward-active region, the Early effect modifies the collector current () and the forward common emitter current gain () as given by:

Only two resistors are necessary for the common collector stage and four resistors for the common emitter or common base stage.

In a common emitter configuration, the negative side of the power supply is alternating current (AC)-coupled to the emitter via a capacitor.

They all together increase or decrease the voltage of the common emitter point (figuratively speaking, they together "pull up" or "pull down" it so that it moves).

Other arrangements of amplifying device are possible, but that given (that is, common emitter, common source or common cathode) is the easiest to understand and employ in practice.

Q3 is a common emitter stage that provides amplification of the signal and the DC bias current through D1 and D2 to generate a bias voltage for the output devices.

A crystal mike picks up the sounds that are fed to the first two transistors of the A1 array connected as an emitter follower driving the remaining two transistors as cascaded common emitters.

The value of the supply voltage is chosen so that a sufficient current to flow through the compensating diodes D1 and D2 and the voltage drop across the common emitter resistor R to be adequate.