TTL Characteristics

Question 1

what are the two sets of dc parameters?

Answer 1

voltages and currents

Question 2

What are the process manufacturing tolerances in DC paremeters and fanout?

Answer 2

V.il, V.ol, V.ih, V.oh

V.il: Guaranteed maximum low-level (L) input voltage allowed for reliable gate operation

V.ol: Guaranteed maximum low level output voltage allowed for reliable gate operation

…anything with an h is “guaranteed minimum high level output/input voltage”

Question 3

v.il-v.ol = ?

Answer 3

low level dc noise margin

same with dc high level noise margin

output voltage transients may venture into the nosie margin region without jeopardizing reliable operation

Question 4

What are the process manufacturing tolerances in DC parameters and fanout as it pertains to circuits?

Answer 4

I.il, I.ol, I.ih, I.oh

Question 5

What is fanout?

Answer 5

a system parameter: number of input circuits one output circuit can drive

Question 6

What is high level fanout equation?

Answer 6

I.oh/I.ih

Question 7

What is low level fanout?

Answer 7

I.ol/I.il

Question 8

As the input voltage Vin falls from +5 volts, the current flowing into the circuit is I.ih, which is what?

Answer 8

the sum of the reversed bias diode current plus leakage.

Question 9

As V.in falls below 1.4 volts, what happens?

Answer 9

the current reverses to become I.il (guarnteed max low level input for reliable gate operation) and the forward diode current begins

Question 10

As V.in falls below 1.0 V, what happens?

Answer 10

the current increases linearly because the diode acts like a .4v battery.

Question 11

I.il is at its maximum when what happens?

Answer 11

input ovltage V.in is at ground (zero volts)

Question 12

If V.in goes negative, what happens?

Answer 12

the input shunt diode turns on when V.in passes .4 v and only V.in source impedance limits the current

Question 13

Why is the input current less than 20 microamperes and less than .4 milliamp at L input voltage?

Answer 13

H and L input currents are very different. This is a cumuliative answer.

Question 14

A shottky clamped output transistor with grounded emitter is equialent to a what?

Answer 14

a resistor as the collector voltage rises from zero with base current fixed.

Question 15

L equivalent output circuit is a .2 v batter in series with a 16.3 ohm resistor

Answer 15

L equivalent output circuit is a .2 v batter in series with a 16.3 ohm resistor

Question 16

V.ol at 0.5 v is the what of the L region? upperbound or lower bound?

Answer 16

is the specified upper bound of the L region

value taken fro a 74LS TTYL low level output characteristic

Question 17

H Level Output: H equivalent output circuit is a 3.6v battery in series with a 92 ohm resistor

Answer 17

H Level Output: H equivalent output circuit is a 3.6v battery in series with a 92 ohm resistor

Question 18

H Level Output: H equivalent output circuit is a 3.6v battery in series with a 92 ohm resistor

Answer 18

H Level Output: H equivalent output circuit is a 3.6v battery in series with a 92 ohm resistor

Question 19

Transistors Q.4a and Q.4b form a darlington circuit. What’s that?

Answer 19

a low output impedance circuit

Question 20

What is a gate transfer function?

Answer 20

It defines the output voltage as a function of the input voltage.

Question 21

When does the output usually change state?

Answer 21

When the input traverses from the invalid region from L to H or H to L.

Question 22

A digital gate is a low-fidelity linear amplifier when the input is in…

Answer 22

in the digital invalid region.

Question 23

What are guaranteed switching speed parameters?

Answer 23

Propagation delay times from gate input transitions to gate output transitions.

Question 24

What are gate output transitions?

Answer 24

Delayed gate input transitions

Question 25

A designer doesn’t pay attention to maximum values for propogation delay times, true or false?

Answer 25

False, they do pay attention.

Question 26

Repeat the following: the setup and hold time requirements are consistent with the assumptions of fundamental mode asynchronous circuit design

Answer 26

Repeat the following: the setup and hold time requirements are consistent with the assumptions of fundamental mode asynchronous circuit design

Question 27

Enabling a connection when connected to the gate load when the enable control changes the output impedance from an open circuit to a what?

Answer 27

to a standard gate output.

Question 28

What is ringing?

Answer 28

damped sinusoidal oscillation following a high to low transition in a waveform

Question 29

how is ringing determined?

Answer 29

by load capacitance, and the inductance of the wiring

Question 30

true or false: damping is set by resistive loading

Answer 30

true, series resistors that are external to a gate output provide additional damping

Question 31

why does ringing limit the switch rate prematurely?

Answer 31

because ther ringing must die out before the next switching transition occurs.

Question 32

Watch for simultaneous switching of inactive outputs. But why?

Answer 32

the voltage induced by ground lead inductance raises the potential of inactive output pins

Question 33

packages with short leads externally and internally significantly reduce inductance. what is inductance?

Answer 33

the property of a circuit or electric conductor to generate an electromotive force by a change in the current flowing. Units are H (henrys)