transistor as a diode

[isanjeev]

can shorting of the emitter and base of a transistor be used as a diode?
emitter is heavily doped as compared 2 base......this will lead to the depletion layer extending more into the base(right?)
will this leave enough of base for proper transistor action?
And what are other ways to make a transistor act as a diode?

 

[keith1200rs]

To use a transistor as a diode you would normally connect the base to the collector.

Keith.

 

[FvM]

To use a transistor as a diode you would normally connect the base to the collector.

To get more than 5 or 7 V reverse voltage, you would rather utilize the BC junction. The emitter must no necessarily be shorted to the base.

 

[isanjeev]

Is shorting of base and collector the only way for a transistor to act as a diode?.......aren't there any other ways?
keeping the emitter open, a small leakage current ( in the scale of µA) would flow.for practical purposes can this current be neglected ? considering that we want the transistor to act as a diode(can the same be considered with the the collector open in the transistor with the emitter and the base connected)

 

[betwixt]

You have not specified the use for your 'diode'. A (bipolar) transistor has two PN junctions, both can be used as individual diodes, C-B or B-E but have slightly different characteristics.
If you want to utilize the full current capability of the transistor, for example if you are using it as a power rectifier, join the B & C together so it conducts and clamps Vf at Vbe.

Brian.

 

[isanjeev]

You have not specified the use for your 'diode'. A (bipolar) transistor has two PN junctions, both can be used as individual diodes, C-B or B-E but have slightly different characteristics.
If you want to utilize the full current capability of the transistor, for example if you are using it as a power rectifier, join the B & C together so it conducts and clamps Vf at Vbe.

Brian.

what are the various ways to make a (bipolar)transistor act as a/any diode (any application)

 

[betwixt]

Transistors are designed to be switches or amplifiers, not diodes so none of the PN junctions are optimized for use as a diode.

Please bear in mind that transistors range from microwave amplifiers to massive current switches and even to multi-kilovolt switches, trying to characterize them in terms of PN parameters simply isn't possible.

Brian.

 

[VATSALA SHARMA]

Can we do this by shorting emitter to collector? In that case Base will be p type and other shorted end will be n type in case of npn transistor. Is it possible?

 

[betwixt]

You are resurecting an old thread but the answer is yes but you only get a low PIV, low-current, high capacitance diode, shorting base to collector and using the emitter as the other electrode will work better in almost all cases.

Brian.