Bilateral or Unilateral

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Hameedulla-Ekhlas

Hameedulla-Ekhlas

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Greeting all,
Can bilateral or unilateral words be used for transistor. Like a diode we call it a unilateral element. How about the transistor?
 
We have a don't ask don't tell policy. :grin:

I would call the transistor unilateral.
 
Hameedulla-Ekhlas said:
I replied one engineer with same answer but he said it is multiple terminal. How you say a multiple terminal element a unileteral.
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I don't know why he was making that distinction unless he was thinking multi-terminal is a blend of bilateral and unilateral properties.
 
He said we can not say a transistor a bilateral or unilateral. He said, when we just consider from collector to emitter it is called unilateral or just any two terminal.
 
I think he is being picky.

Add: they make bilateral and unilateral transistors and diodes.
 
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From page 4 of Basic Electrical Technology
Bilateral Element: Conduction of current in both directions in an element (example: Resistance; Inductance; Capacitance) with same magnitude is termed as bilateral element.

Unilateral Element: Conduction of current in one direction is termed as unilateral (example: Diode, Transistor) element.
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Page 4 of Introduction to Microwave Amplifier Design
Unilateral transducer gain
Sometimes we can approximate a transistor as being unilateral, i.e. there is no reverse transmission, and S12 = 0. If we put S12 = 0 in our expression for Γin, we get Γin = S11. This yields the unilateral transducer power gain of...
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100312-1152 EST

Considerable these:

A transformer is bilateral. Data or power can be transferred in either direction. In fact signal data can be transferred in both directions simultaneously.

A vacuum tube is unilateral. The grid can modulate the current to the plate, but a signal applied to the plate has little effect on the grid.

A synchronous motor is bilateral because it can be a motor or generator.

A fiber optic cable is bilateral, but when an LED and photo diode are added to it the system becomes unilateral.

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I've always seen and used the term 'bipolar junction' for standard transistors, which are basically two diodes.
 
100312-1929 EST

I disagree with the Wikipedia statement that an amplifier with feedback makes it bilateral.

Consider an opamp with negative feedback. The input to this amplifier is a resistor to a summing point, the negative input of the chip, to this same summing point is a resistor from the amplifier output. Theoretically the voltage at the summing point is zero. Therefore, the signal input to the input summing resistor is totally unaffected by any change applied to the output of the amplifier.

If you apply a signal to the output of the amplifier it will not change the output and does not have any effect at the input.

Essentially this opamp circuit is a voltage source with zero output impedance and therefore a signal of finite internal impedance can not change the output of the opamp circuit. In the real world within the normal operating range of this circuit the output impedance is very small.

If an external change at the output of a circuit can not make a change at the input, then it is not bilateral.

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