35
votes
Accepted
Why isn't the BIOS' ROM chip made using CMOS technology?
You're mixing up implementation technology with colloquial terms for functionality.
CMOS - Complementary Metal Oxide Semiconductor - is a method of making logic and related circuitry using both N-...
- 33.4k
34
votes
Accepted
Why do CMOS NOT gate designs differ from BJT NOT gate designs?
However, I've always been perplexed as to why people do not use the former method for chip manufacturing.
In chip design, resistors take up more area than transistors, and area is one of the main ...
- 128k
30
votes
Accepted
Why is there no rolling shutter when using a mechanical shutter?
When I have a camera, that can take still images at 10fps with a mechanical shutter, why doesn't it mean the sensor can take images at 10fps electronically without producing rolling shutter?
In order ...
- 5,092
30
votes
Accepted
Why do we use a CMOS for inverting a circuit when the PMOS already achieves that?
In a word: Efficiency.
You can use a PMOS transistor to drive a logic output high (e.g. VDD) when the input is low (e.g. GND). However, you can't use that same PMOS transistor to drive a logic output ...
- 64.7k
27
votes
Accepted
Why have both: BJT and FET transistors on IC output?
Paragraph 2 of the description says:
FAN3100 drivers incorporate MillerDriveTM architecture for the final output stage. This bipolar-MOSFET combination provides high peak current during the Miller ...
- 171k
27
votes
Accepted
Can I connect two microcontrollers via RS232 separated by a distance of 3.5 inches? Both are on two separate PCBs
If the distance is really 3.5 inches, it is quite absurd to think that when connecting two UARTS together you must use RS-232 tranceivers. You don't need to use RS232 tranceivers and you don't need ...
- 136k
26
votes
Do MOSFET logic gates necessarily need an N channel MOSFET?
Couldn't it be replaced with a simple resistor into ground like this?
Yes it can and is has been done:
PMOS logic
there's also the complementary version:
NMOS logic
We've been there and done that! So ...
- 80.4k
24
votes
Can a NOT gate be used to achieve 180 degree phase shift?
What is 180 degrees phase shift?
When the signal is a sine wave, a 180 degrees phase shift delays the signal for half the period of that sine wave, the sine wave then looks inverted:
Can an inverter ...
- 80.4k
23
votes
Accepted
Why do we need NMOS transistors for NAND gate?
if X or Y on both PMOS transistors is 0 , then both transistors will be open and the output will be 0 because there will be no flow of the current.
The output will not be '0', it will be floating.
...
- 171k
23
votes
Why do CMOS NOT gate designs differ from BJT NOT gate designs?
It's possible to build this circuit with 2 BJT's or one MOSFET
You're reading too much into it.
The difference isn't the technology of the transistor, it's method of circuit operation
In the first ...
- 4,568
21
votes
Accepted
Why is a capacitor used to protect CMOS chips?
That's not a protection device, if you intend "protection" as something that prevents the chip to die, but it serves as a so-called bypass capacitor.
It acts as a reservoir of energy whenever the ...
21
votes
Why is there no rolling shutter when using a mechanical shutter?
There are two parts to this: First, rolling shutter can still occur with (some, see note) mechanical shutters. However, this is only at short exposure times. The shutter is built out of two curtains. ...
- 12.4k
21
votes
Why do CMOS NOT gate designs differ from BJT NOT gate designs?
Your circuit with the bjt is RTL (resistor transistor logic). There’s DTL, TTL, ECL, PMOS, NMOS and CMOS. There’s others as well, but you can research these if you’re interested.
Basically there’s a ...
- 6,090
20
votes
Accepted
Can unconnected inputs make an IC get warm?
Yes, CMOS circuits can get hot when there are floating inputs. You should always connect unused CMOS input pins to a defined voltage, usually GND or Vdd, unless the datasheet tells you otherwise (see ...
- 768
19
votes
Accepted
What does the dashed line between diodes in a CMOS protection network mean?
The dashed line means that the diode is actually distributed across the resistor structure. The resistor is made using a doped region in the silicon, and there is an inherent PN junction between this ...
- 31.3k
18
votes
Why do we need NMOS transistors for NAND gate?
You make the common, and mistaken, assumption that a node that is not actively driven (has zero current flowing) must be at a low voltage. That is not true.
The output of the gate must be pulled down ...
- 31.3k
18
votes
Accepted
Why is this CMOS implementation of XOR wrong?
Have you tried simulating this design to see what it does? (I would not recommend actually building it.)
Recall the basics of n-channel MOSFETs: they will conduct when the voltage at the gate (\$V_G\$)...
- 3,371
17
votes
How to manufacture chip on board?
A custom chip for 10k units is unlikely to be cheap, as the masks will almost certainly cost more than $1k, which means your chip cannot possibly be made for $0.10. The reason the one you've found ...
- 2,881
16
votes
Why does switching cause power dissipation?
Consider a MOSFET switching.
Switching is a transient event, so losses are not usually modeled as "power". Each switching action dissipates a bit of energy. Then you multiply this by the ...
- 71.9k
16
votes
Accepted
Does the 74LVC1GU04 actually have "Schmitt-trigger action" on its input?
This is a copy-paste error. All other (buffered) parts in the 74LVC series have schmitt-trigger inputs, but the 74LVC1GU04 in particular does not. They simply forgot to delete that line from the ...
- 15.5k
14
votes
Accepted
Using CMOS Schmitt trigger inverters in quartz crystal oscillator circuit
A Schmitt trigger inverter is a bad idea for the first inverter which is driving the crystal directly. It may not even oscillate at all as shown, or oscillate at some undesired frequency. Note ...
- 312k
14
votes
Why isn't the BIOS' ROM chip made using CMOS technology?
Back when the PC was first invented, most of the logic on it was power-hungry NMOS and TTL chips. CMOS was very new and the only circuits in the PC that used it were associated with things that ...
- 170k
14
votes
Accepted
MOSFET construction
If a very large MOSFET (i.e. with a very wide channel) was implemented as a single physical device, like the one you saw in class, then the gate electrode would be very long and thin. This would cause ...
- 31.3k
14
votes
Accepted
pull-ups between logic gates
This is a case of interface between logic families (from LS-TTL -to- CMOS). Although both are powered from +5v supply, logic levels differ:
Logic low output for the 74LS93 is compatible with logic ...
- 24.3k
14
votes
Accepted
Why does decreasing the CMOS supply voltage also decrease the maximum circuit frequency?
Decreasing the voltage decreases the maximum frequency that can be used such that the operation of the digital system is as desired.
This is because the equivalent resistance, \$R_{eq}\$, of the CMOS ...
- 2,289
13
votes
Can I connect two microcontrollers via RS232 separated by a distance of 3.5 inches? Both are on two separate PCBs
No, your microcontrollers will not communicate using RS-232 unless you're using RS-232 levels, which only your second option does. What you mean with
(RX, TX, CTS and RTS lines)
is that they're ...
- 90.3k
13
votes
Accepted
Preference of BJT to MOSFET
Not necessarily, MOSFETs are very useful components in discrete applications, too.
For example MOSFETs have lower source-drain voltage drop than BJTs have collector-emitter voltage drop if you have ...
- 1,573
13
votes
Preference of BJT to MOSFET
CMOS transistors on an integrated circuit can be much much smaller (1000's of times) than BJTs. That, together with the ease of driving them (no base current; no need for current limiting resistors) ...
- 18.5k
11
votes
Is the NAND logic gate perfectly symmetrical?
Depends on the environment.
Maybe in your circuit above and in an FPGA they are the same but in an ASIC library you find differences between the various inputs.
- 14.2k
11
votes
Why have both: BJT and FET transistors on IC output?
The CMOS and BJT output stages are combined to from one stage,
the manufacturer calls this a "MillerDrive(tm)".
Why they do this is explained in the datasheet:
My guess is that they want to achieve ...
- 80.4k
Only top scored, non community-wiki answers of a minimum length are eligible