66
votes
Accepted
What is the purpose of a buffer gate?
Buffers are used whenever you need... well... a buffer. As in the literal meaning of the word. They're used when you need to buffer the input from the output. There are countless ways to use a buffer. ...
- 28.2k
27
votes
Accepted
What is the purpose of an AND gate with the same signal on both inputs?
This is a buffer. Two gates means twice the output current. But why use AND gates instead of buffers, you might ask? I was originally going to say that they probably used one or two AND gates ...
- 40.8k
21
votes
Accepted
This op-amp buffer is oscillating and I can't figure out why
Chip suppliers are keen that their users avoid common design errors, shown by application examples in their data sheets. This one is addressed by Linear Technology in their data sheet for LTC6241. It ...
- 24.4k
20
votes
Accepted
Is it a good idea to connect a line buffer to ground?
You should always tie unused inputs to a valid logic level. That could be tied to GND or to the VDD voltage rail. Never leave unused inputs floating in that it can cause excessive power dissipation in ...
- 57k
19
votes
Accepted
Op-amp inverter followed by buffer. Why?
You are right. In most cases this is silly, adds offset voltage, and uses another part. Most likely this is just someone's knee jerk reaction, or blindly following a rule of "always buffer the ...
- 312k
17
votes
Accepted
"Pull-up" and "pull-down" or "push" and "pull"?
Pull-up refers to raising a node to a higher voltage.
Pull-down refers to reducing a node to a lower voltage.
Pull in push-pull refers to pulling current from the load to the transistors.
Push in push-...
- 13.6k
14
votes
Why are BJTs common in output stages of power amplifiers?
MOSFETS used to be more common in power amplifiers, but they were often the lateral type power MOSFETS.
Most modern MOSFETs (Vertical MOSFETs / HEXFETs) are highly optimized for switching and ...
- 356
14
votes
Accepted
Is ping pong buffer the same thing as a double buffering?
No, they are not the same. Both are 'double buffering' in that they involve more than one buffer. However, ping-pong is a specific type, and the phrase 'double buffering' is usually (though not always)...
- 162k
13
votes
Are I/O buffers of ICs design to have 50ohm impedance?
Very few do. If your chip's datasheet does not say it has 50-ohm termination, then it almost certainly does not.
Traditional CMOS and TTL logic does not provide matching termination, though a few ...
- 128k
13
votes
Accepted
Odd 74HCT1G125 behaviour
You aren't allowed to put more than VCC+0.5V on the output pin, even if it's in high-Z state. If you do, you could damage the chip.
What's happening in your circuit is there's a diode connected from ...
- 128k
13
votes
Why are BJTs common in output stages of power amplifiers?
Second Breakdown
(Many) Audio amplifiers operate the output stage in their linear region.
Modern power MOSFETs are not designed to operate in the linear region. Many of them (HEXFETS) are composed ...
- 410
12
votes
Are I/O buffers of ICs design to have 50ohm impedance?
No, the 50-Ohms is not a convention for PCB tracks to carry signals. The 50 Ohms is a standard for coaxial cables and corresponding interconnects - dozens and dozens various SMA/SMB, BNC, type-N, etc. ...
- 39.4k
12
votes
Buffering a Digital Microcontroller Signal for Connecting to an Optocoupler
A simple BJT like MMBT3904 or any switching BJT will do the job. You can get a reel of 100 for two bucks.
- 72k
12
votes
Accepted
Buffering a Digital Microcontroller Signal for Connecting to an Optocoupler
You have many options.
If you need to connect very few optocouplers, you can connect them
directly to the GPIO of your microcontroller (through a resistor), provided that:
You do not exceed the GPIO ...
- 5,317
12
votes
Accepted
Design of a discrete BJT current buffer for low-current op amp
Let's start at the given output driver topology:
simulate this circuit – Schematic created using CircuitLab
On the left is the basic idea, but it is worth some discussion already.
\$C_1\$ ...
- 77.4k
12
votes
"Pull-up" and "pull-down" or "push" and "pull"?
"Push-pull" refers to the current through the load at the output of a pair of transistors placed as a "totem-pole" or one above another.
EDIT: Thanks to the user Chester Gillon ...
- 5,401
11
votes
Op-amp inverter followed by buffer. Why?
It doesn't have much effect on the performance, except to make it somewhat slower because there are two poles in the transfer function.
Chances are the designer only needed the one op-amp in the dual ...
- 384k
11
votes
Why do MCUs typically have so little buffering on the USARTSs?
Your AT91SAM7X256 has 13 DMA Controller channels and 64 KB of RAM. It is more efficient to make the RAM general purpose and use the DMAC to store transmitter and receiver data.
If RAM is instead put ...
- 22.2k
11
votes
What is the purpose of an AND gate with the same signal on both inputs?
The designers have probably chosen the AND gates because of availability or some other such convenience. Maybe they had the AND gates on the bill of materials for that board already.
The gates are ...
- 37.9k
11
votes
Accepted
When do you need buffers/drivers on buses in a microprocessor design?
Large is when the processor cannot drive the various signals properly and that comes down to a number of things but primarily it is the number of devices on the bus.
They all present a load to the ...
- 22.1k
11
votes
Accepted
Why would you use a feedback resistor on a logic buffer?
The resistor adds additional hysteresis beyond what the chip provides. With the nature of what the internet is these days quite possibly you may have found a circuit idea that was designed before the ...
- 57k
11
votes
Accepted
How does a unity gain buffer work?
You've applied the non-idealities of the op amp inconsistently, and have reached a false contradiction. In particular, you've assumed that the op amp has infinite open-loop gain when you concluded ...
- 18.8k
11
votes
Meaning of a buffer in electronics
An ideal voltage buffer has infinite current gain, its output is an ideal voltage-controlled voltage source with zero impedance.
Real voltage buffers of course only have finite (but very high) current ...
- 15.6k
10
votes
Accepted
how to split audio with buffers?
This is a typical powered headphone splitter/amplifier. It is a single gain amp to multiple non-amplifying buffers. The 5.1kΩ Resistors represent the load. As it will be in parallel with your actual ...
- 72.8k
10
votes
Is it a good idea to connect a line buffer to ground?
With any CMOS logic IC, you MUST connect unused logic inputs to a known logic level. You may connect unused inputs to either High or Low, whicever is convenient (or whichever is necessary to make the ...
- 58.1k
9
votes
Op-amp inverter followed by buffer. Why?
The "buffer" is just there to, as the name implies, "buffer" the output.
Since OA1 is part of a feedback network, some of it's output is used already (lost through R2 and R1.) Which means OA1 has ...
- 16.1k
9
votes
What is the purpose of a buffer gate?
Simple buffer gates have a few applications:
In the older days, there where limited fan-out of a logic output, when fed to multiple subsequent inputs. If I remember correctly, it was around 5 for TTL ...
- 16k
9
votes
Accepted
MCU getting powered up through GPIOs
Leave the MCU powered and put it into a sleep mode. Much better practice. Also, you wouldn't need that regulator anymore.
Note that on many datasheets, "Absolute Maximum Values" are defined as ...
- 29.6k
9
votes
Buffering a Digital Microcontroller Signal for Connecting to an Optocoupler
The differential line drivers are not designed for driving LEDs. These buffer chips drive (or receive) a differential signal on two wires. The voltage swing may be 1.3 volts to 1.7 volts. Not enough ...
- 91
Only top scored, non community-wiki answers of a minimum length are eligible