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hayowazzup
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Does anyone know how to measure the input and output impedance of a bjt circuit on Ltspice? eg. a circuit like this
Exactly.vk6kro said:You have real gain if the power of the output is greater than the input. This is the case with most transistor amplifiers. You compare this to a transformer where the power out cannot be more than the input.
Correct, but the product of the voltage gains of the individual stages can never be greater than beta^n where n is the number of stages and the output impedance is equal to the input impedance.vk6kro said:For example, you could follow a voltage gaining common emitter amplifier with an emitter follower.
You have high input impedance followed by a low output impedance. You could cascade these modules as much as you like or until the noise from the first stage is amplified enough to be objectionable.
True, but I would prefer to use a different term for voltage gain due only to impedance transformation. For instance the familiar 20*Log(Vout/Vin) does not apply in those cases and I don't think this is made clear in many EE classes.vk6kro said:Cascading stages is not the only reason to build an amplifier. You may want to drive a meter or a lamp or close a relay. You could drive a FET or the input of an oscilloscope or a frequency counter.
LTspice is a free, open-source simulation software used for electronic circuit design. It has the capability to measure input and output impedance of a circuit by running a simulation and analyzing the results.
Input and output impedance are important parameters to consider when designing a circuit because they affect the performance and stability of the circuit. Impedance measurements can help identify potential issues and allow for adjustments to be made to improve overall circuit performance.
To measure input/output impedance in LTspice, you first need to create a circuit with the desired component. Then, run a simulation and use the .AC analysis tool to generate a Bode plot. The input/output impedance can be calculated by measuring the voltage and current at a specific point in the circuit and using the Ohm's law equation Z=V/I.
Yes, LTspice has the ability to measure both input and output impedance simultaneously. This can be done by using the .AC analysis tool and selecting the "input impedance" and "output impedance" options in the measurement settings.
While LTspice is a powerful tool for measuring input/output impedance, there are some limitations to keep in mind. These include the accuracy of component models, the effects of parasitic elements, and the frequency range of the simulation. It is important to carefully select and verify component models and consider the impact of parasitic elements when interpreting the results.