What Is a Transistor Array?
A transistor array is a component with multiple transistors in one package. Transistors are semiconductor devices used for switching.
The advantage of this component is that it can control multiple output relays and other devices in a small area. If mounted individually, the board area must be designed to be significant, while the board pattern should become long. However, this can cause malfunctions due to noise. On the other hand, transistor array is more economical and functional because they are smaller, lighter, and unaffected by noise.
Uses of Transistor Arrays
Transistor arrays are widely used in microcontrollers. Microcontrollers are control boards that are frequently used in home appliances such as washing machines and are an indispensable part of our daily lives.
Until the advent of transistor arrays, multiple transistors were mounted as a single item. This was not a problem, but space and cost savings were realized after the transistor arrays were introduced. In addition, one no longer had to worry about pattern routing, which reduced design effort and improved noise protection. Today, transistor arrays are essential electronic components on control boards.
Principle of Transistor Arrays
As mentioned above, transistor arrays are electronic components consisting of multiple transistors in a single package. A transistor is a semiconductor device. It is a product of three layers of P-type and N-type semiconductors, and there are PNP-type and NPN-type transistors.
The PNP-type and NPN-type transistors normally behave as insulators in a circuit, but when a voltage is applied to the middle layer, the layers at both ends become conductors. This is how transistors work.
Transistors are mainly used as outputs for microcontrollers. Before the 2000s, bipolar transistors were widely used in transistor arrays. Bipolar transistors were commonly used in transistor arrays before the 2000s because of their ability to conduct large currents and their resistance to noise. Transistor arrays consisting of several of these transistors in a row were the mainstream.
Today, high-speed, low-loss MOSFETs are the mainstream. MOSFET arrays have replaced most transistor arrays.
Other Information on Transistor Arrays
1. Internal Circuitry of Transistor Arrays
There are different types of transistor arrays depending on the transistors used inside.
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DMOS FET: Transistor arrays that can control large currents and have low loss even when used at low currents.
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Single Bipolar Transistor: Transistor arrays that can provide low loss when used at low currents but cannot control large currents.
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Darlington Bipolar Transistor: Transistor arrays capable of controlling large currents, but loss occurs when used at low currents.
There is also a difference in whether the input logic is high active (current flows when a high level is an input to the input pin) or low active (current flows when a low level is an input to the input pin). There are also different types, depending on whether or not a clamp diode, which is necessary when driving a relay, etc., is built in.
2. Source and Sink Type Transistor Arrays
There are two types of transistor arrays, depending on the type of output current, namely: source type and sink type. The source type turns the contacts on and off on the positive pole side of the load. This is the mode of operation in which current is discharged from the transistor arrays toward the load.
On the other hand, the sink type turns the contact ON/OFF on the ground side of the load. The transistor arrays draw current from the load mode of operation.