All Questions
67
questions
1
vote
0
answers
58
views
Can this oscillator possibly work?
I am trying to build a crude RF oscillator. My first attempt, though it simulated fine, disappointingly did not oscillate when soldered together. So, to debug this, I reduced the simulation example ...
- 564
1
vote
1
answer
70
views
Is LTspice AC analysis trustworthy at RF when using low impedance sources?
I'm an amateur at circuit design but I've been reading a lot and trying my best. I've edited the question to try to make the main problem more coherent and add a simple schematic and plots.
My setup ...
- 11
0
votes
1
answer
40
views
Practical Implementation of A Two Quadrant Transconductance Analogue Multiplier [closed]
Currently cannot simulate a functional Two Quadrant Transconductance Analogue Multiplier.
Understood constraints:
Vx is small (Vx << Vt ~ 25mV)
Vy is greater than VBE(on)(0.6V) (a DC offset ...
- 41
4
votes
1
answer
163
views
Design of a BJT Translinear-Based Square-Rooting Circuit
I'm trying to make a simple sqrt circuit to act on an input voltage and provide an output voltage without using log and antilog amplifiers. I'm trying to base my design of the translinear combination ...
- 41
3
votes
0
answers
57
views
Importing BJT model
I am trying to import a model into LTspice for HFA3046 transistor but LTspice doesn't seem to recognize this model. Here is the text for the model from the website:
https://www.renesas.com/us/en/...
- 448
0
votes
2
answers
224
views
Best method to find Zin of a BJT
I am trying to reconcile how to find the Zin of a non-bypassed low frequency (~1 MHz) CE amplifier.
If I google common emitter input impedance I find this (where re = Vt/Ie). Ok, great.
When I ...
- 580
1
vote
2
answers
290
views
RF Circuit shows flat frequency response for BJT amplifier in LTSpice
I am analyzing a signal jammer circuit for prototyping on LTSpice. The amplifier takes a square wave signal input from NE555 IC and is supposed to transmit it at ~2.4GHz using a tank circuit at ...
1
vote
2
answers
177
views
BJT High Frequency Response
I am trying to amplify the FM band (88-110 MHz) from a dipole antenna but my amplifier has no output signal.
My antenna is two lengths of wire that are half-wave resonant at ~94 MHz. One wire (not ...
- 580
5
votes
5
answers
1k
views
How does a current mirror work?
I'm trying to understand how current mirrors work.
In the text book Microelectronics by Jacob Millman, section 3-11, example 3-8, there is a picture of a current mirror:
They said if we consider \$V_{...
- 53
3
votes
3
answers
313
views
Multistage amplifier voltage gain
I noticed if I change AC amplitude for AC analysis the gain changes.
What AC amplitude is the best to use to test for AC analysis to determine gain in general, or is it an end application parameter.
...
- 53
3
votes
3
answers
333
views
LTspice current regulator analysis with MOSFETs and BJT
I ran the transient analysis for the this circuit with NMOS and NPN respectively. Once with the NPN BJT, the results look reasonable. The current through R1 is about 20mA. When I change to NMOS, the ...
1
vote
2
answers
156
views
What stage is required after a unity gain differential pair in this case?
Below is a simple simulation to demonstrate a differential pair operation:
x is the node for V(x) and a and b are nodes for the difference voltage V(a,b).
Vx is the total signal Vd + Vcm. Vd can be ...
- 1,016
2
votes
1
answer
4k
views
How to calculate small signal gain with LTspice?
For my homework I need to find the small signal gains of the circuit below.
For the first part of the circuit the small signal gain is calculated with
$$A_{V1} = \frac{u_{a1}}{u_e}$$
and for all of ...
- 35
1
vote
1
answer
211
views
How to stop sharp transitions of square wave from leaking through transistor
I've simulated a circuit in spice depicted below. The Vin voltage source (on the right) outputs a 100mV pulse every 2 microseconds, and the other voltage source (on the left) is a square wave that ...
- 35
0
votes
0
answers
196
views
LTspice JFET Voltage Divider Bias Configuration
I want to simulate this circuit in LTspice program and find Idss,Vp and Idsq,Vdsq but cannot. How can i simulate transfer characteristic?
- 1