Message	Date	From	Subject
4607	2010-04-29 07:34:39	Nick Kennedy	Squarer circuit for power indication
I was fascinated by a simple circuit in the Fall 2009 QRP Quarterly, taken from KD1JV's web page. It's a simple circuit with some very complicated theory behind it. I did some research on the translinear principle and though I can't say I understood it in depth, it was interesting. Also played with the circuit itself on LTSpice and then by building one on a proto board. My web site discusses some practical aspects of circuit sensitivity to changing certain resistors and a general idea of how to scale the thing for your meter and power measurement. Also links to a discussion of the theory and to Steve Weber's page and his circuit. http://pages.suddenlink.net/wa5bdu/squarer.htm 73- Nick, WA5BDU [Non-text portions of this message have been removed]
4609	2010-04-29 15:18:58	victor	Re: Squarer circuit for power indication
The operation of the circuit is not that complicated. If we refer to the circuit diagram that you attached, when we increase Vin by a small step dVin, current Iy will increase by dIy = dVin/R1 . Q1 and Q3 both have same operating points: same Iy and both have same Vbe=Vce so when Iy increases by dIy both Q1 and Q3 Vbe will increase by the same dVbe which means that Q3 emitter voltage will be more negative by 2dVbe. Q2 operating point does not change by the dVin jump because it receives its bias by R4 resistor, so its emitter voltage will not change. This means that the 2dVbe negative jump at Q3 emitter will appear across base-emitter of Q4. Now we know that Ic of transistors change as exponent of its Vbe, so a jump of 2*dVbe

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4607

2010-04-29 07:34:39

Nick Kennedy

Squarer circuit for power indication

I was fascinated by a simple circuit in the Fall 2009 QRP Quarterly, taken
from KD1JV's web page. It's a simple circuit with some very complicated
theory behind it. I did some research on the translinear principle and
though I can't say I understood it in depth, it was interesting. Also
played with the circuit itself on LTSpice and then by building one on a
proto board.

My web site discusses some practical aspects of circuit sensitivity to
changing certain resistors and a general idea of how to scale the thing for
your meter and power measurement. Also links to a discussion of the theory
and to Steve Weber's page and his circuit.

http://pages.suddenlink.net/wa5bdu/squarer.htm

73-

Nick, WA5BDU

[Non-text portions of this message have been removed]

4609

2010-04-29 15:18:58

victor

Re: Squarer circuit for power indication

The operation of the circuit is not that complicated.
If we refer to the circuit diagram that you attached, when we increase Vin by a small step dVin, current Iy will increase by dIy = dVin/R1 .
Q1 and Q3 both have same operating points: same Iy and both have same Vbe=Vce so when Iy increases by dIy both Q1 and Q3 Vbe will increase by the same dVbe which means that Q3 emitter voltage will be more negative by 2*dVbe.
Q2 operating point does not change by the dVin jump because it receives its bias by R4 resistor, so its emitter voltage will not change. This means that the 2*dVbe negative jump at Q3 emitter will appear across base-emitter of Q4. Now we know that Ic of transistors change as exponent of its Vbe, so a jump of 2*dVbe