In an experiment involving wireless power transfer, I came across voltages of very small magnitude. This needs to be amplified. I don't want to increase the number of turns of the wire and also don't want to use any circuit that uses an extra power source.
How is that possible? It's the violation of conservation of energy... I don't think its possible..
If there is no external power, this means the amplifier cannot amplify power. This would mean that such amplifier would amplify the voltage but will reduce the current in order to keep the input power higher than the output power.
Yes....that is possible..does that mean such an amplifier can be used to drive a lower current rating load/cricuit?
If you don't want a traditional transformer with coils
there is another possibility. You could use a system
of two piezoelectric elements, one as a 'loudspeaker'
and one as a 'microphone', called piezoelectric
transformer, or Rosen transformer.
Another method is a cascade circuit:
http://en.wikipedia.org/wiki/Voltage_multiplier
Of course in either case the energy must be gotten
from the signal itself.
Regards,
Joachim
If you look at the amplifier with the theory of the two-port networks (quadripoles) it won't be hard to estimate a sample device doing what you need, using a T-scheme and it's transmission (ABCD) parameters.
Basically since you want to increase the voltage and reduce the current you need high input current (low input impedance) and low output current (high output impedance). But i don't think you will be able to escape from the use of inductors, although they don't have to be part of a transformer.
Now as i think again, this could probably be achieved without inductors. You need to do some maths.
Consider such T-scheme as the one on the attached image.
For it we have:
Ku=U2/U1=ZL/(A.ZL+B)
Where ZL is the complex impedance of your device which will receive the amplified signal.
For this T-scheme A and B are:
A=1+Z1/Z0
B=Z1+Z2+Z1*Z2/Z0
Let's say you want to amplify the voltage two times (Ku = 2):
Ku=U2/U1=ZL/((1+Z1/Z0)*ZL+Z1+Z2+Z1*Z2/Z0)=2
So then your scheme needs to meet these requirements:
ZL=2*((1+Z1/Z0)*ZL+Z1+Z2+Z1*Z2/Z0)
Of course there are many values of Z1, Z2 and Z0 which would work but, since your input voltage is not sinusoidal and all these equations are for a sinusoidal voltage, it would lead to some nonlinearities of U2. In order to reduce these nonlinearities you need to choose your Z1, Z2 and Z0 according to the carrier frequency of your input signal.
Hmm, a good New Year puzzle:) Boris... a fully theoretical invention? Is it possible?
Indeed Cyril, i made some maths and it's not possible to do that with only capacitors unless we have negative resistance, which means an energy source. Both inductor and capacitor are required.
Yeah... it was the mystery:) But is it negative resistance or impedance (reactance)?
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