Substance:
- Understanding UJT
- UJT refraction
- UJT Function
- How UJT Works
1. Understanding UJT
UJT (Uni Junction Transistor) is a semiconductor component that has 2 doping areas with 3 electrodes, namely an emitter and 2 bases, the resistance between base 1 and base 2 is relatively high, this resistance is called inter base resistance abbreviated as RBB. Its value is determined by the formula:
RBB = R1 + R2It is called Uni Junction because the component consists of only a single PN Junction.
2. UJT refraction
Between base 1 and base 2 is a voltage source (VBB), while the input terminals are E and B1 if IE = 0 / open input terminal, then the resistance between B1 and B2 = RBB (resistance between bases) which is often called ohmic resistance which ranges between 5 kOhm to 10 kOhm.
From the circuit above R1 = resistance between A and B1, R2 = resistance between A and B2, so the magnitude of the ohmic resistance RBB = R1 + R2 when IE = 0, IB1 = IB2 = VBB / RBB, while the magnitude of the voltage at point A is:
VA = (R1/(R1+R2) VBB)
= R1/RBB . VBBThe voltage is called the "Intrisio Stand Off Ratio" voltage, the value ranges from 0.4 to 0.8 volts. This voltage provides reverse bias to the emitter diode, so that the diode is in the off state (not conducting). If the diode is desired to be on, then it must be given a forward bias, namely by providing a voltage of VE> VA + VK, while VK = 'knee voltage diode' or the conductor voltage on the diode and depends on the material.
3. UJT function
As a comparison / adjustment of electrical vibrations such as those found in the oscillator (circuit in the transmitter as a generator of wave carrier signals).
4. How UJT works
IE has not flowed, before VE > VA + VK, after VEB is adjusted up to reach VE > VA + VK, then IE flows because the diode on the UJT is forward biased and works as a conductor, in this condition the resistance of R1 will drop to reach the minimum price, so it can be said that between E and B1 there is a short circuit, this shows that the diode on the UJT functions as a switch, this switch remains closed as long as IE > from a certain value, this is often called "Valley" (IV) for example from the UJT it is known that IV = 6 mAh, then to close the UJT IE must be made > 6 mAh, if not then the emitter diode remains in the open state.