Is a transistor a current source?
A current source is the dual of a voltage source. Active constant current sources are often used in circuits. Often these constant current sources use transistors, although FETs and where applicable, vacuum tunes of thermionic valves can be used as well.
What is current mirror in op amp?
Op-amp current mirror. Current mirrors have relatively high, sometimes nonlinear input impedance, so they must be fed by a current from a high-impedance current source (sometimes known as a stiff current source). An op amp is required if the input current must have a low-impedance sink.
How is the current of an op amp constant?
This voltage drop produces a current given by Ohm’s law of 1.36V / 150Ω, giving a current of 9.1 mA. Even with the addition of a negligible amount of current from the output of the Op Amp (a factor of 100 smaller), the current is constant through the transistor, so the output to the load is 9.1 mA.
Can a voltage-controlled current source be built using op-amp?
In this project, we will explain how a voltage-controlled current source using op-amp can be designed and also build it to demonstrate its working. This type of voltage-controlled current source circuit is also called a current servo. The circuit is very simple and can be constructed with a minimum number of components.
How many transistors are in an op amp?
The op amp is modeled using a subcircuit named OPAMP1. Although the guts of an op amp can contain 20 transistors or more, this model mimics only the higher level (or macro) functions of the device. The result is a simple model requiring only a handful of components.
How to calculate the current in Rsense with op amp?
Plot the input voltage V (2), the voltage across RSENSE V (3) and the voltage across the load V (7,5). If the op amp is doing its job, then V (3) = V (2) = 1V. Now, you can easily calculate the current in RSENSE as I = 1V / 10 Ω = 100mA.