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Transistors
4.3.2.2 AC Current Gain
The AC circuit gain is as follows:
RB
βD RB
A i = β D -------------------------- = -------------------------R B + βD R E RB + βD R E
4.4
BJT Array
BJT arrays are collections of discrete transistors on a single die. They can come in many
variations based on their intended application. The reasons for using an array is that the
devices are more closely matched than a random group of discrete devices (eliminating the
need to sort them), the noise characteristics are better, and the space required on a PCB is
smaller.
There are three types of BJT arrays:
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4.4.1
PNP transistor array
NPN/PNP transistor array
NPN transistor array.
General-purpose PNP Transistor Array
This general-purpose silicon PNP transistor array incorporates two transistors, a Darlington
circuit, and a current-mirror pair with a shared diode.
The two transistors can be used in circuit applications. The total array can be used in
applications in systems with low-power and low-frequency requirements.
4.4.2
NPN/PNP Transistor Array
This general-purpose high-voltage silicon transistor array consists of five independent
transistors (two PNP and three NPN types) on a common substrate, which has a separate
connection. Separate connection for each transistor permits greater flexibility in circuit
design.
Multisim Component Reference Guide
4-10
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