The charge pulser circuits are useful as test inputs for the charge sensitive preamplifiers, as is shown in the first link: the overview. Most of them will contain two files: a schematic file (*.asc) and a symbol file (*.asy). While the schematic diagrams used in the LTSpice models are not the schematics of the Cremat modules, the LTSpice models reasonably reflect the behavior of the Cremat modules.Įach of the links below will download a ZIP file. The LTSpice models offered here were created by LTSpice version XVII. You can learn more about this software and download it here. LTspice is freeware computer software implementing a SPICE simulator of electronic circuits, produced by semiconductor manufacturer Linear Technology, now part of Analog Devices. Bring up the cursors, move them to 100MHz and you can see the impedance looking into the matching network is 50 Ohms with very little imaginary component.LTSpice models exist for many of Cremat's charge sensitive preamplifier modules and shaping amplifier modules. My simulation was designed to match a 50Ohm source to the input of a FET that had an input impedance of 2.1 - j4 at 100MHz. (these instructions should be correct - I am working on a prerelease version of LTspice) I would attach my plot file, but this site won't let me This will save your plot settings (duh!) so you dont have to mess with changing the axes every time you rerun the simulation. Select the plot window (not the schematic window) and do Plot Settings -> Save Plot Settings. This will plot the real and imaginary components. Right click over the left hand axis and change the plot from Bode to Cartesian. Measure the voltage on the left side of C1 and the current going into C1, then divide one by the other to get the input impedance. You should then be able to calculate the impedance matching components (probably a T network) and simulate it.Īttached is a file I am playing with.

Do the same for the output impedance, from the s22 plot. This is the input impedance of the transistor.

set yourself up with a load that has a series 40 Ohm resistor and a series 24.5pF capacitor (which gives -j40 Ohms at 162.4MHz). Looking at the s11 plot on the Smith chart on page 113, it is 40-j40 at your frequency which would imply it is capacitive. While I cannot help you simulate the transistor itself, I can help with the impedance matching. It will be published on the ADI website soon. I am working on an article explaining impedance matching using LTspice and it is based on Chris's book.

Ltspice amplifier