SEMINAR 2
Contents:
- Circuits with diodes
- Voltage Rectifiers
vO
1. VTC for an DR switching port, with ideal diode is:
a) Find the electrical circuit of the switching port to obtain the given VTC.
b) Plot vo(t) for vI(t) triangular voltage, with 3V amplitude and 0V dc component.
c) Considering for diode the constant voltage drop model, with VD=0.6V redraw
the VTC for circuit obtained to point a).
vI
0
2.
a) Derive and plot the VTC vO(vI) of the circuit, for
vI∈[-20V;20V], assuming for D the ideal model. How
does the VTC change if we use for D the constant
voltage drop model?
b) What is the maximum value for vI to have a nonzero output value vO? How does this maximum value
change if we assume for D-the constant voltage drop
model?
c) Plot vO(t) for vI(t) = 5sinωt [V], assuming for D-the
ideal model. What is the application of the circuit?
d) VBias=0. A capacitor C is connected in parallel to R. Assume vI(t) = 5sinωt [V] and D - the ideal model. Replot, qualitatively, vO(t).
D1
A
3. Considering D1 and D2 ideal diodes:
a) Find the expression vY(vA,vB,vC).
b) Plot vY(t) if vC(t)=0; vA(t)=2V; vB(t)=5sinωt [V]. Mention
the states (on, off) for D1 and D2
c) For vC=0V; vA,vB∈{0v;10V}; assuming the logic convention:
0V-“0” logic, 10V-“1”logic, fill the truth table Y(A,B) and find
the logic function of the circuit .
vA
D2
B
R
vB
D1
4. Assume D1, D2 - ideal
A
a) What is the expression of vO(vA, vB)? Determine the value of
D2
vO, the current iR, the states of D1 and D2 and the voltages on D1
and D2 for vA= - 1V and vB = 8V. Draw the circuit’s model in this
B
R
case.
VB
V
A
b) Is it possible to use this circuit as a logic circuit with the inputs
IR
A and B, considering the following voltage levels: 0V – “0”, 10V
VBIAS=3V
– “1”? Where should be the output Y of the logic circuit? Find the
•
suitable value of VBias to use the circuit as a logic circuit with
these voltage levels and give the logic table of the circuit with inputs A, B and output Y.
Y
Vy
vC
•
•
R vO
2K
•
5. D1, D2 – ideal diodes
a) Find the expression of vY(vA,vB,VRef).
b) For vA,vB∈{0V;10V} and VRef=10V, fill in the voltage table and states of
D1, D2 for all combinations of values of vA and vB. What is the logic
function of the circuit assuming the logic convention: 0V-“0” logic,
10V-“1”logic?
c) Find the values of iD1, iD2 and vD1, vD2 for each of the 4 combinations of
voltges vA, vB from (b).
d) For VRef=0V, propose some waveforms for vA, vB to use this circuit as a
full-wave voltage rectifier. What is the sign of the d.c. component of the
output voltage vY?
6. Consider vI(t) a sine wave, 30V amplitude and 50Hz
frequency.
a) How does vI(t), vO(t), and the current through D1 look like?
b) What is the maximum value of the current through D1?
c) Consider that a capacitor C is connected at the output
(between A and B points). What should be the value of the
capacitor so that the output ripple ΔvO < 2V ?
D4
vI
+
•
•
D1
•
•
D3
A
D2
••
RL
vO
0,2k
•
B