Table of Contents
How a BJT transistor can be used as an amplifier?
A transistor acts as an amplifier by raising the strength of a weak signal. The DC bias voltage applied to the emitter base junction, makes it remain in forward biased condition. Thus a small input voltage results in a large output voltage, which shows that the transistor works as an amplifier.
What is a BJT common emitter amplifier?
In electronics, a common-emitter amplifier is one of three basic single-stage bipolar-junction-transistor (BJT) amplifier topologies, typically used as a voltage amplifier. It offers high current gain (typically 200), medium input resistance and a high output resistance.
How do you make an audio amplifier?
An amplifier needs to be designed so that noise at its output remains constant irrespective of the signal. Also, signal to noise ratio should remain high for the entire operating range of the amplifier. So, the amplifier must have a high Signal to Noise Ratio (SNR) which must be a constant over its operating range.
How do common emitter amplifiers work?
The Common Emitter Amplifier circuit has a resistor in its Collector circuit. The current flowing through this resistor produces the voltage output of the amplifier. The Base of the transistor used in a common emitter amplifier is biased using two resistors as a potential divider network.
What is the input signal of a BJT transistor?
The input signal Vin is just a control signal that determines how power from VCC comes out. To be clear, a BJT transistor is a current controlled current source. The current through the collector is proportional to the current through the base. A transistor in a common emitter amplifier only outputs a voltage because of the attached resistors.
What is the difference between BJT and common emitter?
To be clear, a BJT transistor is a current controlled current source. The current through the collector is proportional to the current through the base. A transistor in a common emitter amplifier only outputs a voltage because of the attached resistors. The base current is related to the base-emitter voltage by…
What is the basic transistor amplifier circuit?
The basic transistor amplifier circuit is indicated below: It is called a “common emitter” amplifier since the emitter is common to both the input circuti and the output circuit. There are additionally three capacitors but they do not play a role in the basic transistor amplifier design which mainly involves setting DC voltages.
How to choose an emitter resistor for a transistor?
Let’s start with the value of emitter resistor (R4). The voltage across it should be between 10 and 20\% of the supply (rule of thumb) to give an 80 – 90\% voltage swing at the collector. Decision 1. Let’s take Ve as 10\% of the supply (= 0.5V for a 5V supply). Now choose the current you want through the transistor. 100uA, 1mA, 10mA?