Contents
How does the Zener diode regulate the BJT?
So a low power rated zener diode can regulate the base voltage of the BJT that can pass a huge current through it. In some cases, the zener diode connected to the base of transistor will not provide enough base current. To solve this problem, an additional transistor is used as shown in the following circuit.
Can a Zener be used as a voltage regulator?
This will explore the basic operation of Zener diodes and their use as voltage regulators. They will be used in conjunction with common bi-polar transistors to boost the output current and can used for real-world voltage regulators by students and hobbyists. The following is for information purposes only and comes with no warranty.
How is the maximum current of a Zener diode determined?
The maximum current is calculated by dividing the power rating by the Zener voltage: I=P/V = 3W/12V = 0.25A. In this case, the datasheet specifies 250 mA as the maximum current, so the calculation wasn’t necessary.
Can a Zener be biased in reverse bias?
This article covers the basics of biasing a Zener in the reverse bias regime to create a simple linear regulator. The drawback of the basic regulator, mainly a high source impedance, is overcome with a transistor current buffer. Zener Diode Regulator with Transistor Current Buffers
Can a Zener diode be used as an amplifier?
In some cases, the zener diode connected to the base of transistor will not provide enough base current. To solve this problem, an additional transistor is used as shown in the following circuit. This extra transistor acts as an amplifier.
Can a Zener diode be used for Ripple protection?
The zener diode will provide only moderate protection against ripple voltages. When load impedance varies zener diode regulator does not work effectively. To meet the large load variations zener diode with huge power rating should be used. It will be expensive.
Which is better a BJT or MOSFET circuit?
Even though BJTs have the disadvantages of current-based control, compared to its MOSFET counterpart, BJTs offer many advantages, such as high ESD (Electrostatic Discharge) robustness and low Temperature coefficient for key parameters like VBE and R CE (sat).
What is the power dissipation of a BJT switch?
The source voltage is 5V and the output voltage on the load is nearly 4.958V that is much higher than 4.8V out of a standard PNP BJT. Assuming the load current is 125 mA, we can reduce the power dissipation by the switch by about 20 mW when a low V CE (sat) transistor is used.
What is the temperature of a BJT circuit?
For example, the Base-Emitter Voltage VBE of BJT has a temperature coefficient of about 2mV/K compared to the Gate-Source Threshold voltage of MOSFET that has a temperature factor of about 4mV/K to 6mV/K.