Pulse Generator

Question 1

What is a monostable multivibrator (MMV)?

Other names?

What would be an example?

Draw the U vs. t graph for a MMV.

Answer 1

type of pulse generator

• produces a single output pulse of defined length τ for every trigger pulse
• also: one-shot, monoflop
• ex: defibrillator

Question 2

What are the possible states of a pulse generator?

How can pulses of the same state even be more classified?

Draw the signal amplitude vs. time graph.

Answer 2

resting and active state (effected by signal pulse that exceeds the threshold level = trigger), since there is a forbidden state fast transitions occur and square pulses are generated

⇒ can be stable or unstable (after triggering spontaneous return to stable state)

Question 3

What does time constant τ indicate?

How can it be changed?

Draw a graph.

Answer 3

indicates the time until the voltage on the capacitor decreases to U₀/e value (= active time of pulse)

1. C discharges
2. I decreases exponentially as it flows through R
3. U decreases simultaneoulsy
4. drop under U₀/e ⇒ transition to stable state

⇒ dependend on τ = RC

Question 4

What is an astable multivibrator (AMV)?

Other names?

How is it constructed?

What would be an example?

Draw the U vs. t graph for an AMV.

Answer 4

type of pulse generator

• produces a sequence of identical pulses
• consists of 2 MMVs connected in a ring (trigger each other)
• also: relaxation oscillator, free running multivibrator
• ex: pacemaker

Question 5

Which parameters are restricted to AMVs, hence do not exist for MMVs?

Explain.

Answer 5

• τ₂: since there is a second MMV = time on stable, resting state of MMV₁
• T_AMV: sum of τ₁ and τ₂ = time period
• space factor: percentage of the time period occupied by pulse

⇒ pulse width and inactive time can be adjusted by individual RC elements

Question 6

What is the time of the resting and activated state of a pacemaker?

What is the usual voltage range?

Answer 6

• resting state: 0.8 - 1s
• active state: 0.05 - 2ms
• voltage: 0.8 - 5V

Question 7

What is a bistable multivibrator (BMV)?

Other names?

Name some examples.

Draw the U vs. t graph for a BMV.

Answer 7

type of pulse generator

• requires a trigger for the activation of either of the two stable states
• also: flip-flop, biflop
• ex:
  
  • ON/OFF switches
  • memory units (binaries: stable state 1/0)
  • frequency divider (# pulses = 1/2 # triggers)
  • binary counter array

Question 8

Draw the graph for the binary counter array.

Answer 8

Question 9

How did you calculate energy and charge of one pulse that would get through a tissue?

Answer 9

NOCH AUSSTEHEND