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Questions tagged [cmos]

"Complementary Metal-Oxide Semiconductor" is a process which implements a combination of PMOS and NMOS transistors. Most current digital logic is implemented in CMOS. Its cost-effectiveness due to being so widespread means many other applications have become common as well, such as in analog design, image sensors, telecommunication, etc.

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What' so great about CMOS?

I've read lot of topics here. I read some people saying I prefer to "have CMOS characteristics" & so on , also in some data sheets (like AVR), they say it have CMOS characteristics, etc... I ...
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“Tristate a pin”

What does it mean to "tristate a pin" on a CMOS microcontroller?
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How are CPUs designed?

I've started playing with electronics a while ago and making simple logic gates using transistors. I know modern integrated circuits use CMOS instead of transistor-transistor logic. The thing I can't ...
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Question about mosfet gate resistor

I have n mosfet gate connected to 4043 logic and Id is about 100mA. Both 4043 and mosfet has +5v. I have plan to use 2N7000 mosfet Questions are: How large gate resistor i need between 4043 and ...
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In theory, is it possible to make a logic gate that uses zero current?

CMOS greatly reduces the current draw of ICs because one of the complementary FETs is always in the non-conducting mode, so there is only a flow of current during the transition between states, which ...
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Why is there no rolling shutter when using a mechanical shutter?

So I know it might not be the best place to ask this question, but maybe some of you are familiar with the mechanics of digital mirrorless cameras and the technology of CMOS sensors. I don't quite ...
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Can unconnected inputs make an IC get warm?

I am using an ATF16V8 PLD for some simple glue logic. While testing it on a prototyping board, I noticed that it gets warm to the touch almost immediately. I checked that no outputs were short ...
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MOSFET construction

I've just read an application note and I was confused about this sentence: "Engineers often think of a MOSFET as a single power transistor, but it is a collection of thousands of tiny power FET cells ...
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Precise differences between DRAM and CMOS processes

There are a couple of questions that mention the difference between standard CMOS processes and DRAM manufacture: Why do microcontrollers have so little RAM? How do they integrate logic into a DRAM ...
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Missing Q11 output on 4060

Is there any reason why Q11 is left out on 4060 IC? I've read it was done to extend the max pulse time (highest clock divider) but why was it done on Q11? Why not Q12 and therefore have a full 8-bit ...
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4answers
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Why isn't the BIOS' ROM chip made using CMOS technology?

After reading a computer hardware course on BIOS/CMOS, I'm still unable to determine the reason why the BIOS' ROM chip isn't built using CMOS technology, and why it is connected to a separate chip ...
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Voltage at what Amperage

I've often seen devices with power requirements specified only in Volts (e.g. 7-12V) but never the amperage. I've wanted to run various embedded devices of wall warts and batteries (the devices have ...
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Why do we use a CMOS for inverting a circuit when the PMOS already achieves that?

The output in a PMOS is as follows: I/P O/P 0 1 1 0 Why can't I just use this instead of using a CMOS for inverting logic? (Please ...
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Power consumed by a CPU

I think the power for a CPU with current I and voltage U is I · U. I wonder how the following conclusion from Wikipedia is derived? The power consumed by a CPU, is approximately ...
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Is the NAND logic gate perfectly symmetrical?

In other words: if we swap A and B, will Q behave exactly the same in DC and transient analysis?
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818 views

Is it ok to leave analog switch inputs floating?

Will I run into problems if I leave a few of the analog pins on a CMOS switch (such as the DG409) floating? I know that CMOS digital inputs should never be left floating due to the fact that the ...
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How is this CD4013 application supposed to work?

I'm trying to troubleshoot an issue in a synthesizer I have, an early 80s synthesizer from Roland called RS-09. I'm just starting to study logic and am perplexed by what's going on. In this ...
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How to manufacture chip on board?

I am a developer of a cheap product and i have no experience in mass production. Device is fully functional and represents a single sided PCB, a microcontroller, a bunch of diodes and a few passive ...
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3answers
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Using CMOS Schmitt trigger inverters in quartz crystal oscillator circuit

In all sources I've seen about quartz crystal oscillators using CMOS inverters there's a note like this: But why Schmitt inverter is needed? Won't classic 74HC04 work?
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Are silicon microbolometers inherently more expensive than conventional CMOS light sensors?

We're finally starting to see practical thermal imaging sensors (microbolometers) entering the consumer market. However, they are still vastly more expensive than comparable visible imaging sensors. ...
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What should be considered when sizing trace widths for digital logic signals?

For traces that carry a static DC current, it's pretty easy to calculate the minimum trace width based on the required ampacity of the trace. However, I'm not sure what should be considered when ...
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Fast bidirectional 3.3 to 5V level shifter

For a hobby project of mine, I'm thinking about connecting some old 5V SRAM chips like this one to a 3.3V - capable FPGA. The target frequency is 50MHz. After some simulator experiments I found out ...
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Cascaded logic inverters

In this datasheet the logic diagram shows three cascaded inverters to get a simple inverting function. So that would mean that you have three PMOS-NMOS pairs in succession. Why is this better than ...
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Connecting unused logic gates

Logic gates like AND, OR, NOT etc. often come packed as arrays in ICs. Sometimes not all gates are used in a project. I would like to know how the remaining unused gates should be connected to ...
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4answers
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Should I use CMOS vs. TTL?

Now, I know that this question has been asked so many times that it seems like I'm trolling, but I must point out that I couldn't find the right answer to this question anywhere. So yeah, CMOS and ...
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Tiny 8MSPS DSPs?

I have a problem: I've got five tiny CMOS image sensors (2mm x 2mm), each in a small space (about 10mm x 15mm). They take a clock signal in, and output an analog signal, requiring an 8MSPS ADC each. ...
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1answer
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CMOS transistors for educational purposes

I am currently teaching my daughters Digital Electronics, ages 9 and 12. In doing so, I wanted to introduce them to CMOS logic, since I feel that a hands-on approach is always better than just doing ...
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Can a NOT gate be used to achieve 180 degree phase shift?

I have seen from various sources which say that a NOT gate cannot be used to achieve an 180-degree phase shift. Is this claim true? Edit: The question is definitely sounding unclear because that is ...
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Going from Transistors to Gates to…IC's?

So I am trying to understand I guess what is probably a basic concept of computers. I was taking a look at this previous question: From Transistor to Gates And it's accompanying link: http://www.cs....
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Reliability of anti-static packaging

OK, DILs are on the way out, but from time to time you still can see CMOS DILs packaged like this as ESD protection: That's aluminium foil on EPS (expanded polystyrene). The EPS isn't conductive, ...
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Will multiple chips outputing onto a bus for a few nanoseconds cause damage?

I'm working on a home-brew CPU design, with the usual mix of parallel EEPROMs, static RAMs and registers, tri-stated onto a single 8 bit bus. My /output-enable logic for three tristate-able chips on ...
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5answers
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Why do TTL pulse generators generate an asymmetrical square wave (unlike CMOS)?

I've read that the asymmetrical (about 1/3 mark-to-space) output waveform is due to input gate characteristics of a TTL inverter, but I want to know more about which characteristics of the TTL input ...
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2answers
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CMOS vs TTL Logic Gates?

This is probably a simple question but how come CMOS Logic Gates built from Only Transistors is completely different from one that uses TTL Logic (Like BJT's). I know BJT aren't really used anymore ...
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3answers
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In IC design, what is the Buffer for ?

In CMOS design, we always use two inverters as a buffer, but at some point, I dont quite understand the functions or importances of the buffer. As I was told before, 1) the buffer could smooth the ...
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Which logic gate family is used in a PC? TTL or CMOS?

I read that the propagation delay of CMOS logic gate is longer than TTL; therefore they are not used where speed of processing is important. I thought computers or computer cpu is using CMOS. ...
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walking ring sine wave generator

simulate this circuit – Schematic created using CircuitLab Here is the low pass I have used. I used the 347 op amp just because it was cheap from a local surplus house. I will get discrete ...
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2answers
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What is wrong with this XOR gate built with four transistors?

I try to undestand how to build an XOR gate using discrete transistors. I checked this question with an extensive answer Howerver the xor gate there and also on Wikipedia seems needlessly ...
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1answer
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How do “beyond the rails” analog switches work?

I'm familiar with using CMOS switches ("transmission gates") for switching analog signals, but you can't use them for switching voltages beyond their supply rails. (So if you have a single supply ...
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1answer
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IC Design Resources

Looking for some resources on the design of Integrated Circuit Designs as they can contain a range of components. I am interested in how they can produce diodes and resistors on the dies in the ICs. ...
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CMOS (or CMOS compatible) shift register with latched open-drain outputs

I've been looking for a 3.3V compatible shift register (SIPO) with latched open-drain outputs. I've settled on a 74xx596 (not a '595!), but of all the 74xx CMOS series I've been looking at omit this ...
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1answer
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What to do with unused TTL and CMOS outputs?

Just about everything I've read on the Web, including on this site, say that unused TTL and CMOS outputs should be left floating. However, this TI article, Designing with Logic, states: Unused ...
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1answer
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Q-Point of a circuit

In a BJT or MOSFET circuit we have this curve: What is that q-point? From my research I have the following information: The operating point of a device, also known as bias point or quiescent point ...
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3answers
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Driving LEDs / other small loads with a 74HC06 or similar inverter

I was recently reverse-engineering some firmware (and other bits) from a router, and spotted that the front panel LEDs were driven from a 74HC06 hex inverter gate chip rather than a proper LED driver. ...
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Level shifting in HV CMOS processes

I'm working on a project for which custom ICs are being designed by another person on the project. The process being used is a mixed voltage CMOS process which uses a \$1.8\mathrm{V}/5\mathrm{V}\$ ...
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1answer
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Impact of the channel length on the threshold voltage in CMOS transistor?

Is there a monotonic relation between the channel length and threshold Voltage and is it proportional or inverse?
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Can I slow a CMOS output through an RC filter?

Is it good practice to slow down the slew rate of a CMOS output by putting an RC filter on it? What happens with impedance matching after I do this? Or can I just set the RC filter with such a low cut-...
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4answers
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Thevenin equivalent of nmos

I was reading my textbook(razavi) and came across this circuit where to calculate vout2/vin1 he drew a thevenin equivalent of nmos. I dont understand how thevenin voltage(Vt) and Rt in the equivalent ...
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2answers
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How are the circuits and design considerations for opamps and comparators different, at an integrated transistor level?

I've designed various transconductance and operational amplifiers in CMOS technologies in the past. I've also worked with clocked latching comparators. However, I've yet to design an asynchronous ...
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Raw access to CMOS image sensor?

I am interested in developing an idea using CMOS sensors, and I was wondering if I could get some pointers (I don't know much about image sensors) First, my understanding is that CMOS image sensors ...
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1answer
361 views

on-chip low-pass filter with sub-Hertz cutoff frequency

Sometime ago I had to implement an on-chip (CMOS 65nm) low-pass filter (first order) with very low cutoff frequency (lower than 100mHz). I used PMOS pseudo resistors and momcap, and had to check all ...