Fundamentals of Digital Electronics TTL Circuits

The TTL device is a triode inside, which is a current-driven device, and the input and output must have current in and out; The CMOS device is a MOS tube inside, which is a voltage-driven device that does not require current drive, so it is an ideal device that will not affect the R and C parameters on the periphery of the circuit.

If there is a current outflow from the TTL input, if the ground resistance value is too large, it cannot be guaranteed to be low ( ; The TTL output resistor is too small and the load is heavy, and the output cannot reach a high level ( .

In my experience: 750 R 1K can ensure the normal operation of the circuit, TTL input and output currents are basically fixed values (constants), and the timing time can only be determined by C, which is the case in actual work.

TTL speed is high, can be excluded;

If it is a CMOS device, it is meaningless to choose TTL current to select such a problem, and TTL is unstable with RC timing.

High speed.

Analog integrated circuits, also known as linear circuits, are used to generate, amplify, and process various analog signals (referring to signals whose amplitude changes with time. For example, the audio signal of a semiconductor radio, the tape signal of a VCR, etc.), the input signal and the output signal are proportional.

For example, digital circuit modules (which are responsible for performing logic operations and processing discrete zeros and 1s) are composed of registers and combined logic circuits, which account for a large proportion of the entire system. A register is a circuit structure that can temporarily store logic values, and a clock signal is required to control the length of time the logic values are stored.

The outstanding advantages of CMOS digital integrated circuits compared with TTL digital integrated circuits are: a. Micropower consumption.

a、d。

In fact, in addition to the two items A and D listed above, CMOS circuits have another advantage over TTL circuits, namely high input impedance and large fan-out coefficient.

If there are extra terminals when using TTL and NAND gates, they should not be left empty, and there are the following ways to deal with them:

1.Connect it to the positive end of the power supply with a 1 3 thousand ohm resistor.

2.Connect to high level vh

3.It can be used in parallel with other signal inputs.

PS: The redundant input terminals of the OR OR gate circuit should be connected to the low level. The input terminal of the gate must be connected to a low level.

TTL and NAND gate circuits are redundant.

There are four ways to handle the input:

1. Terminate the redundant input to a high level, that is, connect it to the power supply through the current limiting resistor.

2. According to the input characteristics of the TTL gate circuit, the input voltage is high when the external resistance is a large resistance. This leaves the redundant input empty, and the input is equivalent to an external high level.

3. Through the large resistance to the ground, which is also equivalent to the input terminal external high level.

4. When the working speed of the TTL gate circuit is not high, the signal source has a strong driving ability, and the redundant input terminal can also be used in parallel with the input terminal used.

NAND Gate: NOR Gate (English notgate), also known as inverter, is the basic unit of logic circuit, NAND gate has an input and an output. NAND gates are basic logic gates, so they can be used in both TTL and CMOS integrated circuits.

Aliases: Inverter Scope of Application:

Logic Foreign name:

not gate

Applied Disciplines: Physics Substance:

The basic unit of a logic circuit.

For TTL circuits, the redundant NAND gate is not connected, which is equivalent to a high level, so the NAND gate is redundant can be connected to a high level or floating;

For CMOS circuits, the extra doors are not connected, and the status is uncertain, so it can only be connected to the high level!

Clause.

1. Connect to high level; Clause.

2. Suspension.

Turn it high, if it is NOR gate, it should go low.

In a TTL circuit, the circuit that realizes the line and function at the output end is the "OC gate".

OC door, also known as collector open door, open collector.

Wire and logic, that is, two outputs (including more than two) are directly interconnected to achieve the logic function of "and". In practical applications such as bus transmission, the outputs of multiple gates need to be connected in parallel, and the output terminals of the TTL gates cannot be directly connected in parallel, otherwise the output tubes of these gates will burn out the device due to the low impedance of forming a large short-circuit current (sink current). Hardware, it can be implemented with either an OC gate or a three-state gate (ST gate).

The OC gate should be used to implement the line and, and a pull-up resistor should be added to the output port at the same time.

TTL circuit is the English abbreviation of transistor-transistor logic circuit (transister-transister-logic), which is a major class of digital integrated circuits. It is manufactured by bipolar process, which has the characteristics of high speed, low power consumption and wide variety. TTL circuits are manufactured by bipolar process, which has the characteristics of high speed and variety.

9. What is a totem pole and what is the difference between it and an open-drain circuit? In TTL integrated circuits, the output is connected to 2, line and logic, that is, two outputs (including more than two) can be directly interconnected to achieve "AND".

What is the gate with a ** symbol in the gate circuit? It should be 4 inputs with NAND gates.

Logical relationship with NAND gates: the output is low only when all inputs are high; As long as one input is low, the output is high.

The input terminal is redundant, only one input terminal is used, and the NAND gate is used as an inverting gate (NAND gate), and the logical relationship with the NAND gate is known, (1) and (2) are correct.

1. When the asynchronous input of the flip-flop is active at a low level, if the asynchronous input is rd=1 and sd=0, the flip-flop is directly set to the (1) state.

2. In digital circuits, the commonly used pulse waveform generation circuit is (multivibrator) device.

3. The characteristic equation of the synchronous JK trigger is: (q n+1 = t q n + tq n )

4. In the monostable trigger, one of the two states is a (steady) state and the other is a (temporary) state. Both states of the polyvibrator are (temporary) states, Schmidt touch.

Both states of the emaper are (steady).

5. The input of a certain digital-to-analog converter is an 8-bit binary digital signal (d7 d0), and the output is an analog voltage of 0. If the lowest three digits of the digital signal are "1", the rest are.

0", the output analog voltage is ( ).

6. The main technical indicators of a d and a a converter can be described by two parameters: (conversion accuracy) and (conversion speed).

7. The output of a certain analog-to-digital converter is an 8-bit binary digital signal (D7 D0), VREF=5V, and when the input voltage is, the output binary number is (

8. You can store (8) binary numbers with 8 triggers.

9. After forming a multivibrator with a timer 555, its oscillation frequency f is ( f = 1 t = (r1 + 2*r2)*c).

10. A monostable trigger, the output depends entirely on ("one steady state, one transient, transient when triggered, and will come back again") The input signal only plays a role (trigger).

Content from users: 100 points for teachers.

Digital Circuits1

1. Fill-in-the-blank questions (1 point per blank, 26 points in total).

1.Digital circuits are the study of electrical signals.

2.In digital circuits, when a transistor is used as a switch, it operates in and two states.

3.There are three types of gate circuits composed of MOS transistors.

4.A limiting circuit is also known as a circuit, and a circuit that can clamp the top and bottom of the input signal at a specified level is called a circuit.

6.In the basic rs trigger, r is called the end, and s is called the end.

7.The logical function of the NOR gate is.

8.The operation of the addition of binary numbers is.

9.A flip-flop is a type of circuit that has a function. It has two possible steady states:

state or state. 10.The logical function of the jk trigger is:

11.The characteristics of combinatorial logic circuits are, and the characteristics of sequential logic circuits are:

12.A basic RS trigger is to cross-connect two inputs and outputs.

13.There are three basic logic gate circuits.

15. y=ab＋ab=

2. Multiple choice questions (2 points per question, 24 points in total).

1.If the input variable is n, then the number of combinations of different states of the input variable is ().

a. 2nb. 2n c. n d. n2

2.TTL and NAND gates, the supply voltage is () volts.

a. 15v b. 20v c. 5v d. –5v

3.The logic gate circuit diagram symbol that can realize the a·b=y function is ().

b. abbc. a d. a

b b4.The following statement is correct ().

a.Encoding is the inverse process of the decoder bThe decoder outputs numbers.

c.The circuit that can complete the decoding function is called encoder 10

2. Multiple choice questions (each question.)