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Re: Why do we use "AC1" while doing ac analysis in LTspice ? what does AC1 mean?
Are you referring to the error message below?
No AC stimulus found:
Set the value of a current or voltage source to "AC 1." to make it behave as a signal generator for AC analysis.
You have to select at...
When using more than one op amp, the diodes are superfluous, so I settled on a LTC1151 based VCCS/integrator for driving the LT1210. The circuit shows no oscillation with a voltage input in the range of .1-10 volts with the IRF530, but some of the MOSFETs in the LTSpice library will produce...
Hi ftsolutions,
Thanks for the input. Attached is the LT1050-LT1050-LT1210 circuit I've settled on for fabrication. A basic LT1050 ramp generator is followed by an LT1050 gain stage that drives the LT1210. Since the LT1210 has a reasonable output current and is used with inductive loads, I am...
I do not believe that you can sweep a component value with the AC Analysis in LTSpice, but you can set the start and finish frequencies to 75MHz and rapidly acquire data points for plotting in a spreadsheet by alternately editing the capacitor value in the schematic, running the AC analysis, and...
Your oscillator appears to be an HCMOS device and will be sensitive to loading. The datasheet you provided specifies a maximum capacitive load of 15pF. You have an impedance matching problem. Your signal generator is probably a better match due to lower output impedance than the oscillator...
Hi Klaus,
The two attached images show the simulation with and without the capacitor. With the capacitor, a clean 50 second ramp from 0 to 1.2 amps is achieved. Without the capacitor, oscillation sets in at 1.8 second. As shown in the schematics that I have posted, my circuit is operated from a...
Hi Klaus,
This is a link to the basic ramp generator that I am using with the FET and coil:
https://www.edn.com/design/analog/4438481/Linear-ramp-generator-uses-one-op-amp
D3 conducts when a negative voltage is applied and allows for a triangular waveform, or ramping the current back to zero...
Hi Dick,
As an alternative, I have looked at an LT1210 high current op amp and it is more stable than the LT1793, however, it has a power dissipation of about 800mW and due to its package, it is awkward to assemble it in a circuit and get a good thermal ground. The LT1210 works well by itself...
Thanks for the suggestions. The 1k resistor probably introduced too much of a voltage drop, but I found that a .5uF (or larger) feedback capacitor suppressed the oscillation
Thanks for the response. The clamp diodes provide constant-current charging/discharging of C1 through R1 so that a linear ramp is obtained instead of a sawtooth. I am using LTSpice for simulation and I am not aware of a capability for doing a parametric sweep in conjunction with the AC analysis...
I have simulated an LT1793 op amp/IRF510 FET ramp generator with an inductive load and the simulation oscillates, but the phase magnitude plot doesn't seem to indicate a stability problem (see attached images). If C2 is increased to 1uF, the oscillation is suppressed in the simulation, but I...
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