What are identical transistors?
On a chip we can make transistors that are “identical” in the sense that they have very similar transistor parameters like β and what VBE you get under certain circumstances. This has nothing to do with “external parameters” like VCE because these are mostly defined by the circuit in which a transistor is used.
How do you match FET transistors?
Measuring JFETs
- Get a 5 to 13 volt supply and a DC voltmeter (we used 12V)
- Connect the +V to the Drain.
- Connect the Gate and Source together to a 100Ω resistor.
- Connect the other lead of the resistor to ground.
- Measure the voltage across the resistor, which gives the Idss (1 volt = 10 mA of current)
What is Q1 electrical?
On a circuit diagram, the symbols for components are labelled with a descriptor or reference designator matching that on the list of parts. For example, C1 is the first capacitor, L1 is the first inductor, Q1 is the first transistor, and R1 is the first resistor.
What do you need to know about transistor matching?
Transistor matching with a simple circuit. This guide about transistor matching is specifically about matching a pair of transistors for use in a log converter of a voltage controlled oscillator of a synthesiser. You may also need them in voltage controlled filter designs.
Can you find pair of transistors with nearly equal voltage?
So, the goal is to find a pair transistors with (nearly) equal IS. We cannot measure IS directly, but instead we can pass a known current IE through the transistor, and measure the voltage VBE. Assuming the temperature does not change, matching VBE is then the same as matching IS directly.
When to use VBE instead of transistor matching?
Transistor matching is required in several situations. One is in selecting matched pairs for exponential or logarithmic circuits. Here it is actually the leakage currents that should be matched, but these are difficult to measure without special equipment, so Vbe is often used instead.
Is it possible to use two transistors at the same time?
You can do it with a digital multimeter instead of an expensive digital voltmeter. As you are using two transistors at the same time, if the ambient temperature changes it will be changing for both so wont mess up the results. Ian goes into more detail in his article and you can read it here.