Questions tagged [ota]

The operational transconductance amplifier (OTA) is a type of an operational amplifier which differential input voltage produces an output current.

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The proper way of using gm/Id plot for designing an amplifier or OTA

For any design of an amplifier or OTA, we are given the specs which we need to achieve including: Gain UGBW or 3db BW Slew rate Power consumption Phase Margin Load capacitance I would like to ...
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24 views

PSPICE Error in Second order High-Pass Sallen-Key Filter

As part of a class project, I'm trying to filter pulses with noise by implementing a High-Pass Sallen-Key Filter with the resistors replaced with transconductance amplifiers (schematic shown below). ...
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1answer
101 views

Simulated inductor for guitar use

Edit: Sorry! Please bear with me, this is my first post! Well, it seems that placing a buffer before certain fuzzes can chance their sound. However, placing an inductor after the buffer cancels this ...
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677 views

What's the difference between a generated hex file and a binary file in embedded systems?

I have an STM32 project (let's call it blinky). This project is developed using Keil IDE. It blinks an LED every 1 second. When I build it, a HEX file is generated. Let's say I want to upgrade the ...
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3answers
1k views

Understanding Operational Transconductance Amplifiers

I understand the high-level function of OTAs, that they provide an output current proportional to an input voltage. But what I don't understand, and what I can't seem to find any information on online,...
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1answer
77 views

Determining Phase Boost needed to Compensate SMPS

I'm attempting to find the Control-To-Output Bode Plot (open-loop) of a SMPS designed around the TPS54160 so that I can design the type II compensator. The first step in designing a compensator is ...
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90 views

OTA design, the Gm won't go down to zero

I'm trying to simulate a pseudo-differential OTA, but the the Gm vs Vin(differential) plot I obtain seems warped. The Gm won't go down to zero for large values of Vin. attached is the circuit ...
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1answer
287 views

LM13700 Bias Current via Resistor vs. Voltage-Controlled Current Source

I am trying to understand the advantage of using a voltage-controlled current source (VCCS) to drive the bias current inputs of an LM13700 OTA, compared to a simple application of the control voltage (...
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123 views

Current booster/amplifier for OTA

I am designing an Operational Transconductance Amplifier whose maximum output current should be 15mA. Using Super Class AB amplifier, I was able to get a maximum output current of up to 2mA. The ...
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1answer
96 views

2nd order high pass filter PSPICE error

I'm working on designing a 2nd order sallen key high pass filter in PSPICE for a school project, but in subthreshold with resistors replaced with OTAs (transamp). Schematics shown in figures below. ...
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274 views

How to increase the gain of Operational transconductance amplifier by changing the sizes of transistors.

Here is the schematics of the OTA. By changing the length of the transistors I am having more gain but I cannot reach the gain of 200. The maximum gain I reach is 110.35. I want to reach the gain of ...
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92 views

nRF51822 bricked after faulty boot loader

I have a custom board (a chinese game pad) which uses a chip named n51802, which according to nordic is a “custom” nrf51822 - completely compatible with it though. I “accidentally” (fiddling around) ...
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142 views

State Variable Filter - Unexpected High Frequency Behavior

I am designing a voltage-controlled state variable filter for use in a modular synthesizer. Its function is to produce low-pass, band-pass, and high-pass responses for a given audio input signal. ...
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2answers
385 views

Why cascode transistors contribute little to overall noise in an OTA?

I have read this sentence below in a paper which describes a low noise amplifier. I can't understand the reason why cascode transistors contribute little to overall noise in an OTA?. Can someone ...
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118 views

The current of M5 and M7 of two stage OTA

Let direct current = 100μ,i know the drain current of M3=M4=M6=M1=M2=100μ My question : Is the drain current of M8=50μ ? Oμ ? i think drain current will flow to the gate of M8 dircectly ...
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525 views

How does this CMOS OTA with common-mode feedback work?

In class I learned about the circuit shown below. It is basically a simple CMOS OTA with a common-mode feedback realized by a resistive divider. But I am not quite sure how it works. Lets say that I ...
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117 views

Voltage Reference Question

I'm new to regulators and references and I'm trying to update this old circuit that uses an op-amp as a 2.5V voltage reference. The new circuit will possibly use LM4040, but I'm not sure if it needs ...
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3answers
3k views

Intuitive way to see pole/zero directly from schematic

The image below is the electrical configuration and the transfer function of a type II compensator using OTA. By looking at the transfer function, we can easily see that the circuit has two poles (...
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1answer
172 views

How does CMFB works?

I'm working on simple OTA. I know the purpose of CMFB, I just don't know how exactly in this particular case it works: ppt http://s2.ifotos.pl/img/esepng_ahqpseq.png Common mode voltage increases (...
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257 views

OTA / Common Base (CB) Transistor Circuit

I would like to fully understand the following schematic. Especially the nonlinearities are of interest. (Supply Voltage is +/-15V for both OpAmp and OTA) It's an amplification circuit and the in ...
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1answer
397 views

Do it yourself operational transconductance amp?

While quickly prototyping some of diy-synth circuits I realized that I don't have OTA at hand, but I wanted to continue fiddling with the circuit. Is there a way to make OTA out of op-amps and ...
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379 views

an LM13700 can be configured as a “floating” voltage controlled resistor ; How resistor-like is it?

I want to use an LM13700 as a voltage controlled resistor, and I want it to act like a rheostat. When will it act non-linearly? The description of this circuit is on page 15 of the datasheet, and ...
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1answer
754 views

Help understanding frequency calculation for VCO Schematic in LM13700 Datasheet

I am trying to work through the math of the following schematic pulled from the LM13700 datasheet: I can certainly hook this up and mess with the values to change the frequency range to my liking (...
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2answers
749 views

Voltage Controlled Butterworth Hi-Pass Filter using a Transconductance Op Amp?

In the Texas Instruments datasheets for the LM13700 Transconductance Op Amp (as well as the earlier National Semiconductor versions) there's been an application note showing a voltage-controlled 2 ...
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1answer
2k views

How to use a current source with current control pin of LM13700

I am trying to bias the lm13700 Input amplitude bias current pin with a current source rather than using a voltage source and current limiting resistor as shown in all the data sheet schematics, but ...
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645 views

Is it permissible to use fractional aspect ratio W/L for MOSFETs?

I am designing a 2-stage op-amp (Miller compensated). For compensation, I am using a nulling resistance R in series with the compensation capacitance C, with the resistance implemented using a ...
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1k views

LM13700 Control voltage?

I'm trying to build the circuit shown below. This is a VCA, application taken from Nuts & Volts magazine I think (don't have the article). I know very little about OTAs in general but from what I ...