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PCRT21ASX Datasheet - Page 7

Download or read online AVX Corporation PCRT21ASX Piezoelectric Acoustic Generators pdf datasheet.



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Piezoelectric Acoustic Generators
Amplification Type Circuits
Load Resistance Type
V
R
3
R
1
Q
1
BZ
INPUT SIGNAL
R
2
GND
This is the simplest circuit. Applied voltage V
Loud sound pressure cannot be achieved. For example,
V
=5V
cc
B2=KBS-27DB-3A
f=3.3kHz
R
=30k
1
R
=15k
2
R
=1k
3
V
cc
R
R
3
4
Q
2
R
1
Q
1
BZ
R
R
INPUT SIGNAL
2
5
GND
Two-step amplification using transistors: The transducer is
connected between the collectors of each transistor making
the applied voltage (V
) 2xV
.
pp
cc
Complementary Type
V
cc
Q
1
R
1
Q
1
INPUT SIGNAL
BZ
GND
In this example, the sound pressure level is relatively
low. It is effective for reducing current consumption, and
when a highly efficient circuit is the goal.
Load Inductance Type
V
cc
L
R
1
Q
1
INPUT SIGNAL
R
2
GND
High voltage can be applied to the transducer by using
load inductance. The smaller the “L” is, the higher the peak
voltage. However, the current consumption will increase,
also increasing the spurious oscillation, which results in
degradation of the tone quality.
NOTE: Wherever possible, the piezo devices should be
capacitive coupled to avoid permanent DC bias and possible
long term damage.
6
Oscillation Type Circuits
Blocking Oscillation Type
cc
will be V
.
This is the most effective circuit when loud sound pressure
pp
cc
is required, and the supply voltage is low. This circuit
operates in the same manner as the Load Inductance type.
The duty factor will be large and the spurious oscillation will
increase if the inductance of the transformer is small.
L
=550T (30mH)
1
L
=150T
2
Bz=KBS-27DB-3A
V
cc
1.5V
3.5V
4.5V
CR Oscillation Type
It is easy to generate a sine wave when the high
frequency component is small, which will result in good tone
quality. However, sound pressure is low. The larger the h
of the transistor is, the more stable the oscillation.
Vcc
15.5V
12.5V
9.5V
6.5V
-4.5V
Multivibrator Type
The transducer is connected between the collectors of
two transistors of a multivibrator which generates a stable
square wave. The shoulders of the square wave are
rounded due to this, but V
Vcc
1.5V
3.5V
L
2
V
cc
BZ
L
1
R
1
Q
1
Current
Frequency
R
1
2.2mA
3kHz
38.9k
4.1mA
3kHz
63.7k
6.0mA
3kHz
74.8k
V
cc
150k
1k
0.01 F
0.01 F
0.01 F
1k
BZ
2k
Q
1
2k
Current
Frequency
7.7mA
2.25-3.3kHz
6.0mA
2.25-5.1kHz
4.6mA
2.15-3.0kHz
3.0mA
2.15-2.9kHz
2.2mA
2.05-2.8kHz
V
cc
580
7.5k
7.5k
580
0.02 F
0.02 F
Q
Q
1
2
BZ
will be double V
.
pp
cc
Current
Frequency
3.3mA
2.8kHz
7.1mA
3.2kHz
FE

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