The role of digital transistors

A digital transistor is an electronic component with a built-in resistor in the transistor package.

To turn on LEDs or operate relays through a microcontroller board (such as Arduino or Raspberry Pis), a driver circuit (switch) with transistors and resistors is required. The driving circuit is simple, but it requires a resistor to limit the current flowing through the base.

Due to the built-in resistor in the digital transistor, a single transistor can be directly used to form a driving circuit.

ROHM was the world's first semiconductor manufacturer to develop what is known as a "digital transistor". Nowadays, other companies also sell this type of product called "resistor built-in transistor". For simplicity, it is sometimes referred to as "digi tra".

What is the function of digital transistors

1. When used for amplification, by injecting the base current IB, a current amplified by hFE times can be obtained in the collector IC. In circuit applications, by continuously controlling the collector current through input signals, an output current of hFE times can be obtained.

2. In the function of a switch, it is used in an electrically saturated state when turned on (reducing the saturation voltage between the collector and emitter).

Digital transistors have amplification and switching functions:

(1) When used for amplification, by injecting the base current IB, a current amplified by hFE times can be obtained in the collector IC. In circuit applications, by continuously controlling the collector current through input signals, an output current of hFE times can be obtained.

(2) In the function of a switch, it is used in an electrically saturated state when turned on (reducing the saturation voltage between the collector and emitter).

As a bipolar transistor with an integrated base resistor, a digital transistor mainly serves the following functions:

Switching function: Digital transistors can be used as high-frequency switches to control analog signal switches, digital signal conversion switches, audio and video signal switches, etc. The threshold voltage of digital transistors is low, the collector emitter saturation voltage drop is small, and the switching speed is extremely fast.

Amplification function: Digital transistors can also be used in small signal amplifier applications and as output driver devices. The amplification factor of digital transistors is comparable to that of similar bipolar transistors, while also exhibiting some characteristics of digital circuits, such as lower noise tolerance and the ability to adapt to higher transient voltages and currents.

Triggering effect: For example, in digital circuit applications such as inverters and gate circuits, the triggering effect of digital transistors is very practical. These circuits usually have the characteristic of self adjusting power supply voltage, so they can respond very flexibly to emergency situations.

 As a switch controller: commonly used in DC battery managers, intelligent energy controllers, solenoid valves, etc., to achieve automatic control by leveraging strengths and avoiding weaknesses.

In short, digital transistors have a wide range of applications in both digital and analog circuits. Due to its strong adaptability, wide frequency range, and stable performance, it is widely used and promoted in many fields.