Introduction to 2n2646
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Introduction to 2n2646. It is a uni-junction transistor which is mainly used in thyristor triggering circuits, sensing circuits, and pulse and timing circuits. It features low peak point current of about 5µA, and low emitter reverse current of 0.005µA and passivated surface for uniformity. Let's dive in the details of this transistor and explore what it does and what are its main applications? Let's get started.
Introduction to 2n2646
- 2n2646 is a three terminal semiconductor device that contains only one junction that behaves like an electrically controlled switch.
- This uni-junction transistor (UJT) can not be used as a linear amplifier but it is widely used in triggered oscillators, free-running oscillators, and pulse generation circuits of low frequencies.
- It is composed of n-type semiconductors where p-type material is embedded along its length that helps in fixing the parameter like intrinsic stand off ratio which can be denoted as ?.
- Typical uni-junction 2n2646 contains three terminals named as emitter(E), base 1(B1) and base 2(B2).
- Sometimes it is also referred as a double base diode.
- The base is composed of lightly doped n-type silicon. The emitter is heavily doped and contains p-type material.
- The name of the device is based on the single junction formed between n-type and p-type material.
- When the emitter is behaved as open-circuit, the resistance between B1 and B2 is called inter-base resistance.
- The emitter junction is closed to B2 than B1, so this device doesn't encompass a symmetrical structure.
- Only a fraction of current will flow from B1 to B2 when there is no potential difference between emitter and base terminals.
- However, if large voltage is applied at the emitter terminals then a very large current will flow from B1 to B2 which ultimately generates larger B2 output current.
- The structure of this UJT is quite similar to N-Type JFET, but the gate surface in N-Type JFET is much larger than the emitter junction in UJT.
- This UJT normally functions when emitter junction is forward biased while JFET normally functions when gate junction is reversed biased.
- It is also referred as a current controlled with negative resistance.
2n2646 Pinout
2n2646 is mainly composed of three terminals.
1: Emitter
2: Base1 (B1)
3: Base2 (B2)
- This 2n2646 is designed for industrial applications where circuit economy is taken into consideration.
- It is an ideal choice for firing circuits that are widely used in silicon controlled rectifiers.
Working of 2n2646
- When this device is triggered it allows the emitter current to increase until it is limited by the help of emitter power supply.
- It can be used as an oscillator because it exhibits a negative resistance.
- This UJT gets biased when positive voltage is applied between the two bases. It will cause a potential drop in the device.
- The current will start to flow from emitter to base region, when emitter voltage is exceeded one diode voltage above the voltage where diffusion of P-type material occurs.
- This additional current at the base region allows the resistance between emitter and B2 lead to decrease, hence overall improves the conductivity of the device.
- This resistance drop will make the emitter junction forward biased which helps in injecting the more current.
- This drop in resistance makes the device operate over negative resistance that's why it is useful for oscillator circuits.
Absolute Maximum Ratings
Absolute maximum ratings of 2n2646 is shown in the figure below.
- Stresses above than the given values can damage the device.
- Also if stresses are applied for extended period of time above normal operating values, they can effect the device reliability.
Electrical Characteristics
Electrical characteristics of 2n2646 are shown in the figure below.
- It is important to note that these electrical characteristics don't effect the performance of the transistor.
- The 2n2646 is mainly manufactured for the purpose where low peak point emitter current, and low emitter leakage current is required.
Applications
- 2n2646 is mainly used in pulse and timing circuits.
- It is a building block of thyristor triggering and sensing circuits.
- Free-running oscillators and pulse generation circuits with low frequencies use this UJT because it exhibits negative resistance.
That's all for today. I always try to sort out information into small steps so you can digest the information easily. I hope you have enjoyed the article and got a clear idea what this UJT does and what are its main applications? However, if still you feel skeptical or have any doubt you can ask me in the comment section below. I'll help you according to best of my expertise. Stay Tuned!