Upload
hidayah-kamaludin
View
239
Download
0
Embed Size (px)
Citation preview
8/10/2019 L7 Clipper Clamper Logic Gates
1/13
Clipper and Clamper Circuits
8/10/2019 L7 Clipper Clamper Logic Gates
2/13
Clippers
Clipper circuits, also called limiter circuits, are used to eliminate
portion of a signal that are above or below a specified level.
The level here is referred to as clip value, V. To find V, use KVL
at L1
The equation is : V VB- V= 0V = VB+ V
Then, set the conditions
If Vi > V, diode conducts, hence Vo = V
If Vi < V, diode off, open circuit, no current flow, Vo = Vi
L1
Vi
V = VB+ V
8/10/2019 L7 Clipper Clamper Logic Gates
3/13
Clippers
Other clipping circuits can be constructed by reversing the diode,
or the polarity of the voltage VB.
V = VB- V
conditions: Vi > V off, Vo = Vi
Vi < V conducts, Vo = V
V = - VB+ V
conditions: Vi > V conducts, Vo = V
Vi < V off, Vo = Vi
V = - VB- V
conditions: Vi > V off, Vo = Vi
Vi < V conducts, Vo = V
8/10/2019 L7 Clipper Clamper Logic Gates
4/13
Parallel Based Clippers
Positive and negative clipping can be performed simultaneously
by using a double limiter or a parallel-based clipper.
The parallel-based clipper is designed with two diodes and two
voltage sources oriented in opposite directions.
This circuit is to allow clipping to occur during both cycles;negative and positive
8/10/2019 L7 Clipper Clamper Logic Gates
5/13
EXAMPLE 1
Consider the parallel clip circuit shown below.
Assume the VZ1= 6V and VZ2= 4V and V=
0.7V. Given vi = 10 sin t, sketch vO
8/10/2019 L7 Clipper Clamper Logic Gates
6/13
Clampers Clamping shifts the entire signal voltage
by a dc level.
Consider, the sinusoidal input voltage
signal, vI.
1st 900, the capacitor is charged up to
the peak value of Vi which is VM.
Then, as Vi moves towards thevecycle,
the diode is reverse biased.
Ideally, capacitor cannot discharge,
hence Vc = VM
By KVL, we get
NOTE: The input signal is shifted by a dc
level; note that the peak-to-peak value is
the same
8/10/2019 L7 Clipper Clamper Logic Gates
7/13
Clampers
STEP 1: Knowing what value that the capacitor is charged to. Using KVL,
VC+ VBVS= 0 VC= VMVB
STEP 2: When the diode is reversed biased and VCis already a constant
value
VOVS+ VC= 0 VO= VSVC.
A clamping circuit that includes an independent voltage sourceV
B.Peak value VM
8/10/2019 L7 Clipper Clamper Logic Gates
8/13
EXAMPLESclampers with ideal diode
C
+
Vo
-5V
+
Vi
-
Vi
t
-10
10
Vi
t-8
10C
+
Vo
-5V
+
Vi
-
Step 1: VC- VBVi= 0 VC= 10 + 5 = 15V
Step 2: VOVi+ VC= 0 VO= Vi15.
-5
-25
8/10/2019 L7 Clipper Clamper Logic Gates
9/13
What if the diode is non-ideal?
C
+
Vo
-5V
+
Vi
-
Vi
t
-10
10
The diode is a non-ideal
with V= 0.7V
Step 1: VC+ V
+ VBV
i= 0 V
C= 10 + 50.7 = 14.3V
Step 2: VOVi+ VC= 0 VO= Vi14.3.
-4.3
-24.3
8/10/2019 L7 Clipper Clamper Logic Gates
10/13
Multiple Diode Circuits
8/10/2019 L7 Clipper Clamper Logic Gates
11/13
DIODE ID VD
OFF 0 VD< V
ON ID> 0 VD= V
8/10/2019 L7 Clipper Clamper Logic Gates
12/13
OR GATE
V1 V2 VO
Vo = voltage
across R
D1 and D2 off; no current flow, 0 0 0
D1 off, D2 on, current flow,
VoV2 + V= 0
0 5V ( 1 ) 4.3V
D1 on, D2 off, current flow,
VoV1 + V= 0
5V ( 1 ) 0 4.3V
Both on, using both loops will
give the same equation
5V ( 1 ) 5V ( 1 ) 4.3V
8/10/2019 L7 Clipper Clamper Logic Gates
13/13
V1 V2 VO
Both on, using both loops will
give the same equation
0 0 0.7
D1 on, D2 off 0 5V ( 1 ) 0.7
D1 off, D2 on 5V ( 1 ) 0 0.7V
Both are off; open circuit no
current flowing through R since
no GND destination
5V ( 1 ) 5V ( 1 ) 5V
AND GATEVo = node
voltage