What is a transistor current source?

What is a transistor current source?

A current source is the dual of a voltage source. Current sources can be used to bias transistors and can also be used as active loads for high gain amplifier stages. They may also be used as the emitter sources for differential amplifiers – for example they may be used in the transistor long tailed pair.

Why we are using PNP as current source?

Here the amplifying transistor is connected to ground; so, the active load should be a source whose output “pushes” a current into the collector/drain. Its output is the collector/drain; so its emitter has to be connected to +V. That is why this arrangement (kind of connection) requires a p-n-p (PMOS) transistor.

What power sources are needed by the transistor?

The transistor is used as a switch (ON or OFF) and produces an amplifier with good efficiency. These are often called switching amplifiers or switch-mode amplifiers. The circuit is operated from a dual-rail power supply where +VS is positive power supply voltage and –VS is negative power supply voltage.

Why BJT is called current controlled device?

A BJT is a current controlled device because its output characteristics are determined by the input current. A FET is voltage controlled device because its output characteristics are determined by the Field which depends on Voltage applied.

Why transistor is called current amplification device?

Transistor 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.

Is battery a current source?

A battery is a voltage source, not a current source. Some terminology: what you attach across a source is often referred to as a “load”. Ideal sources are independent of load.

Does voltage or current control a transistor?

Transistor are current controlled devices which control the flow of current thru a load, not voltage. The voltages measured in a simple single stage amplifier are due to the current flowing from the positive terminal to the negative terminal of the current source that is powering the amplifier.

How does current flow through Transistor?

Because a transistor’s collector current is proportionally limited by its base current, it can be used as a sort of current-controlled switch. A relatively small flow of electrons sent through the base of the transistor has the ability to exert control over a much larger flow of electrons through the collector.

What is the source of leakage current in a transistor?

The subthreshold leakage is the drain-source current of a transistor during operation in weak inversion (where transistors switch ON though the gate source voltage is below the threshold voltage, the voltage at which when exceeded the transistor is expected to be turned ON).

What is transistor current?

A transistor regulates current or voltage flow and acts as a switch or gate for electronic signals. A transistor consists of three layers of a semiconductor material, each capable of carrying a current. A semiconductor is a material such as germanium and silicon that conducts electricity in a “semi-enthusiastic” way.

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