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Loop gain greater than 0db – In a typical feed-forward operational amplifier or for that matter any other negative feedback system, on countering a scenario where the loop gain of the system is greater than 0 dB and phase is -180 degree, one usually opts for Nyquist analysis to discern stability. Even though this proves that the system is stable, is there an intuitive explanation as to why those frequency points where the gain is higher than 0 dB and phase -180 degree on a bode plot doesn’t keep on adding to itself and lead to instability? Read more
Distorted/deformed output signal downconversion mixer – I am designing a down conversion mixer for a wireless transceiver course. I started with just a simple single balanced mixer to get to know the basics. The circuits (mixer circuitry and test bench) are shown below. A mixer multiplies 2 sines. The result should look like this. However, I noticed that my output is somewhat different. This is the output of my circuit when feeding it with a (sufficiently large) 900MHz LO and -20 dBm 918MHz RF signal:
You can see that the 18 MHz down converted signal has some strange deformations around the peaks of the signal (marked with a red circle). I increased the power of the RF source, to look if this changes the case, and it only made it worse. When I changed the power of the RF source to 0 dBm, the differential output signal of the mixer became:
As you can see, the deformation/distortion increased significantly. I was thinking about what the cause could be and come up with the following explanation (and that is my actual question): Would it be a fair assumption to attribute this distortion to the (mainly second order, namely the square law) non-linearity of the V to I converter (tail current source MN2)? Read more
Adding and simulating audio amplifier IC to Proteus – I am working on audio amplifier circuit; the same as the audio amplifiers used at the headphones but with a different IC, the LM4840 I use Proteus for the simulation but this IC is not included at the Proteus library. I have added it, but when I simulate, it doesn’t get connected to the other components and doesn’t simulate the circuit. Read more
LM331 circuit not working – I found LM331 datasheet and tested Fig.14 in breadboard. It works well. But when I tried the circuit as per Fig.16, I find no output. Any advice? Read more
Many LNA design questions – I can understand that in the LNA, the opamp is used to gain up the noise, using LPF + HPF as bandpass, then measure as the amplified noise output. I took some time to create simulations to try them as I have never made any active filters before using an opamp. I want to understand more about the opamp criteria. Here come all the questions….Read more
Level shifter or analog amplifier for level shifting – I have a 1.8V digital output, and I want to drive 75Ω input with that at at least 3.3V. What is the best solution ? Also I need 5ns at the most rise and fall time. Read more
Threshold voltage of MOSFET – I was working on 32nm NMOS. However, I am finding it difficult to find the approximate threshold voltage of the MOSFET. Can anyone suggest a circuit to find the threshold voltage? Read more
Verilog, an error while using Spectre via Virtuoso – While running a .Va file using Spectre, this error happened.
Error(Vacomp-2259) “voltage G1<<–? G2, G, temp;
For this line:
Voltage G1, G2, G, temp;
Can anyone help? Read more
Battery working principle of electron flow – If I connect a battery across a semiconductor current is this current flowing due to flow of electrons in the semiconductor, or due to the sum of electrons provided by the battery plus the semiconductor? Read more
Dual voltage mechanical switch – I have two different Vin lines (12 V and 24 V) and I need a pushbutton switch. Now, I have found a 1no1nc push button switch and I am not sure it right. Appreciate if any of you experience fellows can advice what technical definition I need to look for to get the right pushbutton switch? Read more