Questions tagged [analog]
Analog circuits have a range of voltages, rather than just two as in digital logic.
3,761 questions
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Differential-mode gain for mismatched \$g_m\$ in differential amplifiers
[Source of figures and equations are Design of Analog CMOS Integrated Circuits by Razavi]
I am struggling to figure out how to derive this red-border expression of differential mode gain. He states to ...
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Analyzing the following current mirror
I came across the circuits below in one of the videos on the YouTube channel All Electronics. It was sketched on the whiteboard.
YouTube Video: THD - Total Harmonic Distortion
I have tried to ...
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Common Mode Range in comparators
What do we mean by Common Mode Voltage Range in comparators, and how does it help in selection of a comparator for any application?
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How can I measure a 0-3.3V analog signal through an isolation barrier?
I am running into an issue where I have to be able to receive an analog DC voltage that will vary from 0-3.3VDC, but I need to be able to isolate the signal before I run it through an amplifier and a ...
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Is wider component spacing on a PCB less noisy? [closed]
As a general case is it true that an analog board with components spaced out is less noisy than one with a more compact layout?
I am specifically referring to a 4 layer board with power and ground ...
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How to know status of a component?
If a part is NFND (not for new design) on for example in Octopart but active in Avnet, Digikey and Mouser, how am I suppose to know what is up?
Can I use this part or not? I mailed the manufacturer ...
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Analog auto balance bridge method for finding impedance of unknown
Hi all, I'm trying to find impedance of unknown (DUT - Inductor) with analog auto balance bridge method. I'm bit confuse about its working procedure, so need to know more about its working procedure. ...
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Metal Strip current sense Resistor layout
I am using a current sense resistor in my design. I have a question regarding which end of the resistor to be used for connecting to sense amplifier. The footprint and the connection diagram is given ...
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Why does my DC motor make whining noises when I try to drive it with a motor driver?
I want to drive this motor with this driver in a microcontroller project, but all I get is a loud whiny noise so I did some investigations and pinpointed my issue down to the driver.
My current (...
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Inference of analog neural network in LTspice
I am attempting to replicate the XOR model described in the paper "Training End-to-End Analog Neural Networks with Equilibrium Propagation" using LTspice. Specifically, I am using the ...
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Can I control multiple parallel LED drivers with one analog signal?
I want to dim some hundred LEDs with analog dimming (current control, not PWM). There are various LED drivers that are able to analog dim. Two examples: A6211 and AL8860. Can I control about 20 of ...
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Telescopic cascode amplifier design
I was following a tutorial from youtube and learning about double ended telescopic cascode 2 stage amplifiers. I was curious to know how to modify this circuit to get single ended zwo stage telescopic ...
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Contradiction while solving for gain
I have been trying since long to find out the differential and common mode gain of this circuit. From my knowledge about analog design, in differential mode, the tail node goes to virtual ground, and ...
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How quanitization levels in ADC are adjusted?
I understand Quantization in an Analog-to-Digital Converter (ADC)
refers to the process of converting the continuous analog signal
into discrete digital values.
For example: To change the radio ...
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Frequency response of 5 transistor OTA
I need to calculate the open loop zeros and poles for this system.
What I tried is at some node between Gm2 and Gm1 block there will be one pole and value of effective capacitor is the capacitor which ...
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Finding Gain of the Analog circuit
I have been finding the input referred noise of the circuit shown below. Here, I am using this approach, please correct me, and help
I found out the output referred noise of the circuit to be \$ 4KT\...
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What really happens inside ADC chip? [closed]
I know analog signal is input and output of ADC is 0100100001...
Wikipedia and other sites shows me a graph of Digital out vs. analog in.
I am mature enough to ...
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Understanding noise in analog circuit
I have been wondering in this analog circuit when we try to find out the input referred noise, how I went about is, I first found out the output referred noise power spectral density. I modelled a ...
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Designing a single ended Operational Transconductance
I am working on designing a single-ended Operational Transconductance Amplifier (OTA) with the following specifications in 180nm technology using LTspice:
DC Gain: > 65 dB
Unity Gain Bandwidth: >...
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What is the right way to check a MOSFET's SOA curve?
I'm trying to figure out if a P-MOSFET can handle 2A of current in DC.
I've already found two ways to check it based on the MOSFET SOA curve.
I'm using the FDS4685, with 24V input. I need to know if ...
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Why is the output not stable in the given circuit?
I have constructed an audio amplifier using a TIP 127 pair in class A type (circuit below). The output sound (power) keeps decreasing as time passes and is not stable. This is also measured by a ...
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Why I am seeing peaking at NMOS switch output?
I am designing a simple switch using an NMOS. The NMOS P/N is PMV65UNE. The circuit is given below.
I am observing a peaking at the output of the MOSFET. Please see the below image.
Below is the ...
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Resistor connected to comparator non-inverting input
I came across such a circuit.
When a voltage above 0 is applied to the noniverting input, the output remains at 3.3v. So far, normal.
When I pull the input directly to gnd in the pspice simulation, ...
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Identifying pole/zero frequencies in an op amp stabilization In-the-loop compensation circuit - Analog Devices article
I have been reading the following article by Analog, which discusses methods used to stabilize op amps when driving capacitive loads.
Analog: Practical Techniques to Avoid Instability Due to ...
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Scaling down the voltage [e.g. +/- (50V to 3.3V)] and shifting it from bipolar (+/- 3.3V) to unipolar (0 to +3.3V)
VG1 is an AC (sine wave) signal with a voltage of ±50V. I need to scale down this voltage and shift it from bipolar (±3.3V) to unipolar (0 to +3.3V) using an op-amp. The op-amp should operate with ...
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Normalizing voltage circuit
Given input voltages \$\{ V_{x 1}, V_{x 2}, \ldots, V_{xn} \}\$, we want to
obtain output voltages \$\{ V_{y 1}, V_{y 2}, \ldots, V_{yn} \}\$ such that:
Each output voltage \$V_{yi}\$ is proportional ...
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Saturating BJT in emitter follower
Can we saturate the BJT in emitter follower configuration by increasing base current? If yes, what happens in the process? How does increase in collector current decrease \$V_{CE}\$ when there is no ...
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Current source with low drop out voltage
I am using this circuit to provide 10mA for some LEDs connected in series.
It regulates fine, but the problem is that the voltage drop is about ~3V, meaning that I cannot connect more LEDs or, I have ...
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Is it possible to make a constant DAC controlled current source using LT3092
I am trying to make a constant current source using LT3092 .My DAC maximum output is 3.3V and at that time the current source needs to generate a current of 20mA.
For generating 20mA the RSET(R1 in ...
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DAC Based current source not working as expected
I am designing a DAC controlled current source based on this material. My DAC maximum output voltage is 3.3 V. Maximum output current is 20 mA.
But I am getting only 2.3 μA. My circuit is given below.
...
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Questions About Logic Analyzers: Mixing Digital and Analog Signals
I recently became interested in logic analyzers, particularly those like the Saleae models that can sample both digital and analog signals on the same channel. I understand that for analog signals, an ...
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Why can it be that connectors do not cause reflections when they are short enough?
I've always followed the usual guidelines but I can't help but having this question at the back of my mind: it is generally acknowledged that if connectors are shorter than 1/20th of the wavelength of ...
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Active bleeder circuit design clarifications
I was learning about bleeder circuits from this source.My question is about item number 5[An Alternative].
The circuit diagram is given below.
In the description you can see that "The major ...
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Finding short circuit transconductance of a differential pair with passive load (current mirror circuit as load)
From Behzad Razavi's "Design of Analog CMOS Integrated Circuits", Chapter 5.
I wish to find the short circuit transconductance \$G_m\$ of the above circuit.
\$G_m = \frac{I_{out}}{V_{in}}\$....
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Opamp output current spec, what is meant by VDROPOUT?
I am using ADA4077 in one of my application. I was checking it's output current specification.
It is given below.
My question is,
What you mean by VDROPOUT here?
What is the significance of VDROPOUT ...
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A circuit to dim an LED whenever it gets dark
I want to make a circuit to automatically control the brightness of an LED.
I want the LED to be at its brightest when it is brightest outside, and to start dimming as it becomes dark outside.
I was ...
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Lead-acid battery charging circuit
"This schematic is for a lead-acid battery charger circuit. I've set up this circuit, but it's only charging at about 15 milliamps. Can anyone help me troubleshoot this problem? By the way, all ...
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Problems with specific case of Blackman formula for calculating input impedance
I was reading a book about basic CMOS circuits ("Analog Design Essentials", W. Sansen) and I stumbled uppon this ciruit where input impedance \$z_{in}\$ is to be calculated.
I tried using ...
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Convert MBF Band pass to differential band-pass
The problem
I need to design a differential to single-end band-pass filter & amplifier before an ADC (sampling at 8kHz) :
DC-blocking
0dB at 60Hz
10dB (ideally 20dB) for frequency above 120Hz
-...
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Interfacing MCP3550 ADC to ArduinoMega at Vref, VDD, Vin+ = 4.8 vin-=0, not getting reading of 4.8 on serial monitor, code is below, what is reason?
I'm getting reading on serial monitor as 1.2V Max and adc reading of 1042017, for different vref too adc reading is stuck at 1042017 so i think there is some bits missing during transfer may be? and ...
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Solving differential equation using opamps
I have a first order differential equation with initial value problem:
$$ \frac{dy}{dt} =\frac{a}{b} \cdot x(t) - c \cdot y(t) $$
with initial values of $$ y(0) = (\frac{a}{b} \cdot c) \cdot x(0) $$
...
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Opamp noise analysis corner frequencies calculation
I am learning about opamp noise calculation in this document.You can see calculation example:1 in page no:7.
Below equations are used for calculating the corner frequencies.
The calculation are given ...
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Why simulation result of BSP129 by PSpice is not the same as in practice?
I want to make a current limiter circuit using the "BSP129" Transistor.
I have made a simulation file using the cadence software and found this component in its Pspice library.
In practice, ...
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Is there an AC powered circuit to turn on load only if the power switch is toggled at least once before being switched on (Not using an MCU)?
I have a project where the requirement is that if a light switch is turned on, one load will be turned on, but if the switch is toggled first before being switched on, a second load will be powered as ...
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White Noise Equivalent Bandwidth (NEB)
This question is regarding White Noise Equivalent Bandwidth (NEB).I was going through this material from Renesas .
The definition of NEB is given as when running white noise through a first order low-...
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Does channel length modulation take effect in triode region of MOSFET?
AFAIK, the channel length modulation (CLM) effect only occurs in the saturation region due to the shrinking of the channel \$(*)\$. So, in ideality (\$\lambda=0\$), the \$I_D-V_{DS}\$ characteristic ...
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Why won't this new current mirror work?
This basic current mirror is well known:
It has its flaws, such as failure to deal with channel length modulation since \$V_{DS_1}\$ is not same as \$V_{DS_2}\$.
As well as, external circuity above \$...
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PT100 smart sensor design - protection PT100 input against 24V DC
I'm trying to design a smart PT100 sensor and I would like to protect the 3-wire PT100 input against accidentally applying 24V DC. Is my solution work correct and protect the op amp, ref3030 and the ...
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Why opamp noise gain is referred to non inverting input
I was learning about noise analysis of opamp with the help of this document.It says that for Noise Gain In op-amp circuits, noise is commonly assigned to the non-inverting op-amp input.
But no ...
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Why is power good used like this in this application?
My understanding is that power good signal is normally used to pull down the reset pin of the main microcontroller when you have a power issue like overcurrent or any other power problem with the ...
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