mV level transformer

[okbro]

Can toroidal transformer be used with input signal of say 200mV amplitude and 2khz frequency at the primary to get stepped up output at the secondary? Does such level of voltage amplitude require thin wires?

 

[ronsimpson]

Transformers can handle low voltage. Some microphone amplifiers have a transformer in the input. The signal is much smaller than 200mV. The wires are small but they don't have to be.

 

[rjenkinsgb]

Can toroidal transformer be used with input signal of say 200mV amplitude and 2khz frequency at the primary to get stepped up output at the secondary? Does such level of voltage amplitude require thin wires?

Yes, if the core material is suitable for use at that frequency.
Note that the impedance changes with the square of the voltage ratio, and obviously the power at the output will be slightly less than at the input.

Some simple intercom circuits use a small output matching transformer (intended to drive a loudspeaker in a small amplifier) "backwards" with a loudspeaker connected to the low impedance side and the high impedance side then gives an output similar to a dynamic microphone - though with the frequency response somewhat limited by unconventional use of the speaker.

Note that the majority of audio frequency transformers use conventional laminated E-I core construction rather than being toroidal style, though toroids are used occasionally.

eg.

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Small signal ones are often screened, such as this:

http://www.hammondmfg.com/pdf/140NEX.pdf

 

[crutschow]

Does such level of voltage amplitude require thin wires?

The wire size is determined by the winding load current and the number of turns, not the voltage.

 

[okbro]

Audio transformer exists and they have lots of turns and thin wires. But I have not seen toroids in audio frequency range. Is there any limits on frequency range for using toroids and size of wire diameter relating frequency range, wire diameter and size of toroids?

 

[Nigel Goodwin]

Audio transformer exists and they have lots of turns and thin wires. But I have not seen toroids in audio frequency range. Is there any limits on frequency range for using toroids and size of wire diameter relating frequency range, wire diameter and size of toroids?

There have been toroidal valve output transformers in 'modern' times, no different to square output transformers.