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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a conventional
circuit, FIG. 2 is a characteristic diagram showing general impedance characteristics of a
piezoelectric vibrator, and FIG. 3 is a characteristic graph showing frequency characteristics of
the conventional circuit. Fig. 4 is a circuit diagram showing one embodiment of the piezoelectric
buzzer self-oscillation circuit according to the present invention, Fig. 5 is a characteristic diagram
comparing the frequency characteristics of the circuit of the present invention with the
characteristics of the conventional circuit, Fig. 6 It is a characteristic view which compares the
temperature characteristic of the invention circuit with the characteristic of the conventional
circuit. 11 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·. Series resistance, C ..... capacitor.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric
buzzer self-oscillation circuit which is used as a piezoelectric pregnancy tool. Conventionally,
various self-oscillation circuits using pressure have been proposed. The circuit shown in FIG. 1
was representative. That is, in FIG. 1, (Ill is a pressure 1, a pressure t8 work that becomes a
buzzer, and the collector-emitter junction of the transistor (Tr) is connected, and its return R1
[pole is the base series resistance (R2) v Connect to the base of the transistor (T,) via Also, (R1) is
a bias resistor of the transistor (T,), and (RL) is a load resistor. In the above configuration, when a
terminal (V, c) K DC power supply Y is applied, a suitable bias is applied to the transistor (T,)
through the resistor (R,) (R,) 1, and the feedback of the piezoelectric buzzer + Ill The oscillation
operation is performed at a predetermined resonance frequency by applying a feedback voltage
5111 ′ ′ ′ from the electrode. However, in this circuit configuration, there is a drawback that
the range of the self-oscillation is narrow with respect to the variation in the characteristics of
the earth-child pregnancy element 1111 as the piezoelectric buzzer. Here, in the soil 1 ink mover,
as shown by the impedance characteristic of FIG. 12, there are a plurality of colliding points, and
the impedance of these becomes lower as the frequency rises. In addition, the self-excitation of
the piezoelectric buzzer-Ifi should be generated at the frequency of retroactive primary
resonance point (jol), or a piezoelectric mirror (1 year-old co-imaging point Cf, 2 due to the
variation of 111, etc.) The subsequent resonance may be stronger than the resonance of -f1
order. Therefore, in this case, if self-oscillation is performed in the circuit shown in t1, it will be
missed at the one-year and second-order co-grip frequency. Also, if # shooting is weak as a
whole, 1 oscillation operation? There is also no case. That is, 131 P. The circuit of the logic
diagram (in which the frequency characteristics of the circuit including the feedback electrode
are measured and the characteristics such as 3) are shown (α is small when R2 is small and 1 is
large when R2 is large Y As apparent from this characteristic, the gain of the # 憑 point Cj02-fO
4-one) after the second order is higher than the gain near the first resonance point (f,...). In
addition, if the value of the base series resistance (R2) is set small enough to facilitate oscillation
at the primary resonance point Cf,. The gain after 1 year and 2nd order is added. It can be said
that this is a circuit that easily oscillates at resonance points after one year old second order *
vyt. The purpose of the present invention is to reduce the gain in the 1 ili range [increasing the
gain at the 1st resonance point as V enables the oscillation operation at the 1st resonance point
to be stabilized.
Piezoelectric oscillator-Response of self-tumor development to variation of 4! The present
invention is to provide a piezoelectric buzzer self-excitation excavated road 1 which has a wide
range V. The present invention will be described below with reference to an embodiment shown
in FIG. The parts corresponding to those of the figure 1 will be described with the same reference
numerals r. In the illustration. The piezoelectric vibrator +111 serving as a piezoelectric buzzer is
connected between the collector and emitter of the transistor (Tr) which is an amplifying
element, and its feedback electrode is connected to the base of the transistor (Tr) through the
base series resistance (u2) v . The collector of the transistor (T,) is connected to the base via the
bias resistor (R1) and the base series resistor (R2) t '. Connect KjX, capacitor av between this
collector and base. Furthermore, the load resistance (RL) is connected between the collector and
the power supply terminal ff, and the emitter is grounded (5). Here, the N series base shield (R7)
is a piezoelectric actuator αD111) fIIk The input impedance Y of the circuit seen from the return
electrode is increased, and the feedback voltage applied to the base of the transistor (Tr) is
divided by the base series resistance (R2) and the input impedance hiφ of the transistor (T) .
Conden 曽 0 has a gain Y that lowers the high-pass gain Y, and has a spring r to promote the
numbering at the first-order colliding point (9,). That is, since the gain in the 1% region can be
reduced by connecting the capacitor C), the value Y of the base series resistance (R2). It can be
made smaller than the conventional one to add gain v at the first order passthrough point (f,,).
Therefore, its frequency characteristic is 11! As shown by the line. The gain at one year primary
collision point (61 (fo)) is increased compared to that shown by the conventional broken line, and
furthermore, the gain at collision point <102′′f05− ′ ′ ′ ′ after second order Falls to
large @. Thus, in operation, at the base of the transistor (T7), at the frequency of .chi.1 resonance
point Cf,). Sufficient feedback voltage will be added, and rooting operation at this frequency will
be stabilized-As a result, the pressure response range of the mobile terminal to the pressure 8
will be broadened, and the temperature characteristics will also be shown in Figure 6 It could be
stretched T to <-20 ° C as shown. As mentioned above, compared with the conventional circuit,
the operation of the piezoelectric buzzer automatic @ acetabulum by one consideration becomes
extremely stable by the excessive addition of the capacitor 1 iliil on one part. The range of
application for piezoelectric imaging is wide (and its effect is large in practical use.