Since the bipolar transistor is a classic three-point, there are three possible ways of its inclusion in the electronic circuit with a common entry and exit output:
- common base (OB) - high voltage transmission coefficient;
- common emitter (TE) - the amplified signal as a current and voltage;
- common-collector (OC) - amplified signal current.
In each of the three types of circuit switching transistor, it reacts differently to an input signal, as the static characteristics of its active elements depend on the specific solutions.
scheme with a common base is one of three typical configurations incorporating bipolar transistors.Usually it is used as a current or voltage amplifier buffer.Such schemes enable transistors are characterized in that the emitter is acting as an input circuit, an output signal is taken from the collector and the base of "grounded" to the common wire.A similar configuration are switching circuits FET amplifiers with a common gate.
| parameter | expression |
| Koeff.usileniya current | Ik / Iin = Ik / Ie = α [α & lt; 1] |
| Bx.resistance | Rin = Uin / Iin = Ube / Ie |
circuits of transistors ON different stable temperature and frequency properties, which provides a low dependence of their parameters (gain of voltage, current, input impedance) of temperatureconditions of working environment.The disadvantages of the scheme include small Rin and no current gain.
circuit with common emitter provides a very high gain and provides an inverted signal at the output, which can have a pretty big spread.The transmission coefficient in this scheme largely depends on the temperature of the displacement current, whereby the actual gain is somewhat unpredictable.These schemes enable transistors provide high Rin, the current gain and voltage inverting input, ease of switching.The disadvantages are the problems associated with overdrive - possibility of spontaneous positive feedback distortion occurs for small signals due to low input dynamic range.
| parameter | expression |
| Odds.current gain | Iout / Iin = Ik / Ib = Ik / (Ie-Ik) = α / (1-α) = β [β & gt; & gt; 1] |
| Bx.resistance | Rin = Uin / Iin = Ube / Ib |
scheme with a common collector (in electronics, also known as an emitter follower) is one of three types of circuit switching transistors.It is fed on the input base circuit, and the output is removed from the resistor in the emitter circuit of the transistor.Such a configuration of the amplifier stage is usually used as a voltage buffer.It serves as the base of the transistor input circuit, the emitter is output, and a grounded collector serves as a general point, hence the name of the scheme.The analogs may serve as the connection type field effect transistors with a common drain.The advantage of this method is relatively high input impedance of the amplifier stage and a relatively low output.
| parameter | expression |
| Odds.current amplification | Iout / Iin = Ie / Ib = Ie / (Ie-Ik) = 1 / (1-α) = β [β & gt; & gt; 1] |
| Koff.voltage gain | Uout / Uin = URe / (Ube + URe) & lt;1 |
| Bx.resistance | Rin = Uin / Iin = Ube / Ie |
All three standard circuits of transistors are widely used in circuit design, depending on the purpose of the electronic device and the conditions of its application.
