# Questions tagged [logic-gates]

Symbolic representation of ideal devices implementing boolean functions

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### create sr_latch from gates in verilog

consider this file : tb_sr_latch.v ...
480 views

### Diodes needed (parts) for OR gate automotive relay circuit

I need to power up a make-or-break simple automotive relay (4pin, 40A 12V) via an OR gate. OR gate as follows: Source 1 is the cable that provides +12V to activate car dome light which I will tap ...
1 vote
469 views

### How can I implement this function with JK flip-flop + NAND gates?

I need to design a mod-5 up/down counter with control input x. When x = 0 it will count down, and when x = 1 it will count up. I'm allowed to use only a JK flip-flop and NAND gates. Complement of x is ...
1 vote
93 views

### Master-Slave JK Flip Flop Truth Table

In my computer logic and design class, we have gone over the different types of flip flops and their representations. I understand what the goal of the master-slave configuration is but I am having ...
39 views

### Help needed Creating a truth table and a logic circuit using a statement given [closed]

i have gotten this question in my assignment, i'm quite confused about this and don't know where and how to start doing it, any help is appreciated
1k views

### How to convert logic gates to multiplexer in a circuit?

In one of my previous questions, I wanted to know what integrated circuit I could use to replace my logic gates in the circuit below: The accepted answer helps me to redesign my circuit and replace ...
405 views

### How does a two input transistor AND gate work?

I'm trying to self study electronics. I started reading a book on digital electronics and I got stuck on the first chapter. It's about the logic gate circuit. There is a two input AND gate circuit ...
2k views

### Do MOSFET logic gates necessarily need an N channel MOSFET?

I've been studying CMOS logic gate design, such as an inverter here: Why do we need the N-channel MOSFET at the bottom at all? Couldn't it be replaced with a simple resistor into ground like this?
37 views

### How do I make a gate with only one condition?

I need a simple gate with one condition only but with two ends, if its given 10V it will deliver a square wave from an oscillator I've built, if not then it will deliver a wave from a signal generator,...
38 views

### 9T SRAM Circuit Supporting 1-bit Multiplication

I was reading a paper that added a 3T NAND gate, consisting of two NMOS and one PMOS, to the regular 6T SRAM, achieving 1-bit multiplication. However, I'm struggling to understand how the NAND part of ...
4k views

### I keep coming across the term "bubble pushing in logic gates."

Can anyone please simply explain to me what it is? A simple little lesson or answer would be appreciated.
1 vote
266 views

### SR flip-flop with Preset and Clear should not work as described

In the presented flip-flop, suppose the Enable signal is high, the S is low, and R is high. Now we set the Preset low (0) and the Clear high (1). In this condition, we expect Q=1 and Q'=0. But ...
2k views

### Is there any way to know how real discrete components are being connected to each other using logical gates?

Let's say we created some gates or something with VHDL. How can I convert that code into those diagrams that show how discrete components (such as transistors and resistors) are connected to each ...
1k views

### Logisim shows output as X, even though the gate is connected

Below is a basic NOT circuit using a NAND gate. Not sure why output is X, when I change Output properties to three state no, I can't modify circuit. Sometimes, these issues go away when I restart ...
1 vote
165 views

### Tri-state buffer, why is it called high-impedance?

I found this picture of a tri-state buffer: When the enable signal is 0, the output is disconnected from the voltage sources. But why is this called high-impedance? From what I understand impedance ...
1 vote
131 views

### 12 transistor XOR CMOS gate

I have come across this circuit for an XOR gate (see below) using 12 transistors in CMOS technology. I am having trouble understanding the circuit, mainly in identifying the logic gates. I know that ...
406 views

### Logic gate biasing a BJT (again)

The following schematic shows a PNP BJT driven by the output of a logic gate. When the logic gate output is high the transistor must be off, and only be activated when the logic goes low. The problem ...
84 views

### How do I make a gate diagram for $a'c'+abc+ac'$? [closed]

I have checked with the program Logic Friday and it checked the shown gate diagram, which showed me another result and came with this gate diagram: Is this the correct answer?
1 vote
502 views

### Can I implement addition and subtraction in different operations using a MUX?

I'm building a 16-bit ALU that needs to be able to perform logical AND, OR, add, subtract and rotate one bit to the left. I need to have addition and subtraction operate with different op codes ...
53 views

### 555 timer and JK flip-flop activation problem

I need to toggle a MOSFET after I hold a button for 3 seconds. Here is my circuit: I have a JK flip-flop for the toggle function. When the clock pin of the JK flip-flop goes high to low, output of ...
23 views

### Why would I use HNM (high noise margin) gate drive over a TTL gate drive for DC motor driving application?

I am making a very simple half bridge DC motor drive using the MAX1760 gate driver. Looking through the datasheet I saw that it offers two types of logic level technologies (if that's the right word?);...
72 views

### Is it possible to create a logic gate design for a clocked D flip-flop register where there is a synchronous reset and an enable pin?

I'm currently designing a register where there needs to exist a data input pin (DIN), Clock (CLK), Reset (RST), and a RUN pin. The register is designed such that, only at positive edges of the clock ...
265 views

### Does taking dual of a boolean expression also result in its complement?

I was revisiting XOR and XNOR and the form of their different equations. XOR = A ⊕ B = A'B + AB' I took the dual of it: Dual of XOR = (A'+B) (A + B') = AA' + AB + A'B' + BB' = AB + A'B' This is ...
397 views

### RS (NOR) flip flop stuck at undefined

I'm trying to make an asynchronic automata which outputs every other impulse (any amount of 1's) from input ( 0 in any other state).Heres states table: ...
444 views

### Unknown logic gate on circuit

I'm studying the CMI decoder circuit from Maniatopoulos, Antonakopoulos and Makios, 1995, but I can't understand some symbols in the diagram. They look like a small logical OR. Can anyone tell me what ...
1 vote
55 views

### Which is the preferred circuit layout? Horizontal vs. Vertical (Combinational logic)

I have 2 equivalent circuits Picture 1 (Compact, a bit messier) Picture 2 (Easier to read, less compact)
1 vote
616 views

### Design this memory with D flip-flops

Design the following memory with D flip-flops (you can use other gates or decoders if needed). The following memory has 4 one-bit locations and can access 2 locations at each moment and read from ...
233 views

### I need to make an OR-gate

I have 3 kOhms resistors, one voltage (5 V), 2 switches so I can control my input. Can someone help me? I need to do like this: I have done this so far:
330 views

### Please explain how this XNOR gate works

As S1 is 1 (5 V) and S2 is 0 (0 V) then D1 is conducting, D3 and D4 are reverse biased, and D2 is conducting. Q1 is switched over and shuts the output to 0 V via D2 and S2, etc. All states. Could ...
1k views

### FPGA: How do LUT's change their logic

I've looked at a couple of posts on this topic, but I can't really get a feel to them. Does the LUT have an input where the logic address is given, or does the LUT read from the D Latch? If anyone has ...
245 views

### Multi-level circuit simple NAND conversion: Why keep non-NAND symbols?

I am working on understanding the NAND conversion. I have just got the basics of two-level NAND conversion, and when I went to the book example for a multi-level NAND conversion it used solved an ...
1 vote
3k views

### Finding the SOP expression for the XOR gate and the circuit for it

Would the sum of products expression look like so: $\overline{A}\cdot B+A\cdot\overline{B}=Z$ ? And the corresponding circuit should look like so? Sorry for the bad drawing. I'm just wondering if ...
1 vote
53k views

### Designing a 4-bit adder-subtractor circuit

I am designing a 4-bit adder-subtractor circuit using CMOS technology. The instructions I was given for the design portion are as follows: Given two 4-bit positive binary numbers A and B, you are to ...
81 views

### How do I integrate this MOSFET NOR logic gate with my circuit?

I have got an H bridge circuit controlled by a bridge driver (not in the schematic here). I want to control the disabling of it cutting of the conection to ground. I need the logic of a NOR gate but I ...
110 views

### Output of a logic gate when its inputs are floating

As per this answer, the output of an OR gate when one of its inputs is 1 is 1 regardless of the other inputs, even if they are floating/disconnected. However, what is the output of an OR gate when ...
154 views

### 7404 IC Always outputting high

I'm new to electronics, and it's my first time using a hex inverter. The following pins are connected: 1(Input A)-GND or VCC 2(Output A)-LED 7-GND 14-VCC VCC is 5V, but whatever I do the output is ...
80 views

### Clock logic for 8-bit computer

I have been in the process of remaking Ben Eater's 8-bit-computer, and have a few questions. I got to the part where the clock, which consists of 3x 555 timer, is connected with logic gates. However, ...
1 vote
920 views

### Tail Light Control State Diagram

I am attempting to implement this tail light design first by using a state diagram. The car has 4 tail lights on each side, making a total of 8. They behave accordingly when the following inputs are ...
107 views

### Diodes for implementing digital logic

This diagram in this post is from Microelectronic Circuits by Sedra and Smith. The question corresponding to this picture asks to write a truth table with A and B as inputs and X and Y as outputs and ...
1 vote
201 views

### A high-voltage logic part in PSpice

I'm trying to build the following part of a circuit: I'm wondering what the part is that has "HI" written on it; I couldn't find it in any PSpice guide.
74 views

### Wired AND and OR question, logic levels?

In the "wired AND and OR" gates pictured can anyone explain what the voltage levels will be for each function? For AND, I see the output is A*B and for OR, A+B. Is this correct? Also, is ...
1 vote
105 views

### How to turn an LED on in an inverter circuit

I am currently trying to build an inverter circuit which turns on an LED (on a simulation before building it physically). I am using an 2N3904 NPN transistor, 5V voltage sources, a 220k and a 47k ...
1 vote
588 views

### Time (Propagation delay) taken for adding 3 n-bit binary numbers using Carry Propagate Adders (Ripple carry adders)

While being introduced to carry save addition technique, I was told that the time taken for adding 3 n-bit binary numbers using ripple carry adders will be (2n+1)t_FA (Assuming we neglect the minor ...
193 views

### NAND and NOR gate, question on choice and function

I see both described in following images 1, 2 and 3. Does anyone know why image 3 has more transistors? Also, the basic advantage to using NAND or NOR gates in digital electronics? 1. 2. In the ...
6k views

### Convert And-Or Gate to only NAND Gates

I have to create a two level circuit NAND only gates for the Fibonacci from 1-8. After creating a truth table and K-Maps, I got the Function F=A'B + B'C. Then I drew the AND-OR circuit and tried to ...
298 views

### Which of these is the correct circuit for JK flip-flop

Are both of these correct ? I am seeing both of these in different places
1 vote
94 views

### Using a logic driver with a 50 ohm load

I have a load which is an external trigger input of the Highland Technology T130 single-channel picosecond EOM driver (technical manual - Google Drive link) which is 50 ohm and it requires a pulse ...
1k views

### Connecting input and output to the same bus

I'm reading "But how do it know". And in register chapter, it talks about connecting both input and output pins to a bus. I tried to do it on Logisim but it shows red wires. Can someone ...