Logarithmic Converter, Control Voltage to Logarithmic Current, Part 2, Implementation

Here's an image of the logarithmic converter built on a copper plane.

Logarithmic converter

The measurement cables measures I_C2, from converter to ground. The two PNP transistors are glued together for better thermal stability. The IC is a dual op amp, LM358P.
The following table shows I_C2 as a function of V_C.

VC(V)	Simulated IC2 (mA)	Measured IC2 (mA)
0	0.027	0.031
1	0.055	0.064
2	0.110	0.130
3	0.220	0.268
4	0.443	0.551
5	0.871	1.02

I think simulated and measured data compares pretty good, considering that simulation is done using general op amp model, and not the right transistors. I_C2 doubles pretty well with every voltage step. We really don't need exact values, since a calibration pot will be added as soon as the VCO is up and running. The next post will be about building the VCO.