Other Parts Discussed in Thread: TINA-TI
Hi all,
I'm new to Tina-ti, so thanks in advance for any help you may be able to give me.
I have simulated the drive stage for an amplifier of a real circuit for a unit which checks conductivity of boiler water. The unit uses a constant amplitude drive of a 1kH (400mV p-p) triangle waveform signal into a load, with a feedback loop to ensure that the signal is always constant as the resistance of the load or wiring losses change (from a few ohms to several k).
In the simulation I have used a signal generator to produce a triangle waveform of 68mV p-p at I/P of the amplifier, and this produces a constant O/P of 400mV p-p (as the real unit does).
The simulation works fine & gives me the same results as the real unit. But I need to make some changes to the amplifier, but before I do I would like to try & look at what the phase margin of the loop is.
Here's my issue, if the I/P is 68mV & O/P 400mV, this gives a fixed gain of around 15.92dB and I I double the sig gen amplitude, the O/P doubles accordingly. But the AC Transfer Characteristics tool (see below), shows the gain as never getting much above 0dB.
The first plot below is for a load is for a load of 220Ω & a simulated cable resistance of 100Ω. The second plot is for a load of 22Ω & a cable resistance of 10Ω.
Am I being stupid here & not seeing the wood for the trees here ? So any help would be brilliant.
Hope this is sufficient detail, but I can load the cct if that would help.
Many Thanks
William B
