HA17339

` Square-Wave Oscillator
    The circuit shown in figure one has the same structure as a single-voltage power supply astable multivibrator. Figure 2 shows the waveforms generated by this circuit.
` Pulse Generator
    The charge and discharge circuits in the circuit from figure 1 are separated by diodes in this circuit. (See figure 3.) This allows the pulse width and the duty cycle to be set independently. Figure 4 shows the waveforms generated by this circuit.
` Voltage Controlled Oscillator
    In the circuit in figure 5, comparator A<sub>1</sub> operates as an integrator, A<sub>2</sub> operates as a comparator with hysteresis, and A<sub>3</sub> operates as the switch that controls the oscillator frequency. If the output Vout1 is at the low level, the A<sub>3</sub> output will go to the low level and the A<sub>1</sub> inverting input will become a lower level than the A<sub>1</sub> noninverting input. The A1 output will integrate this state and its output will increase towards the high level. When the output of the integrator A<sub>1</sub> exceeds the level on the comparator A<sub>2</sub> inverting input, A<sub>2</sub> inverts to the high level and both the output Vout1 and the A<sub>3</sub> output go to the high level. This causes the integrator to integrate a negative state, resulting in its output decreasing towards the low level. Then, when the A<sub>1</sub> output level becomes lower than the level on the A<sub>2</sub> noninverting input, the output Vout1 is once again inverted to the low level. This operation generates a square wave
on Vout1 and a triangular wave on Vout2.
` Basic Comparator
    The circuit shown in figure 6 is a basic comparator. When the input voltage V_IN exceeds the reference voltage V_REF, the output goes to the high level.
` Noninverting Comparator (with Hysteresis)
    Assuming +V<sub>IN</sub> is 0V, when V<sub>REF</sub> is applied to the inverting input, the output will go to the low level (approximately 0V). If the voltage applied to +VIN is gradually increased, the output will go high when the value of the noninverting input, +V<sub>IN</sub> *R<sub>2</sub>/(R<sub>1</sub> + R<sub>2</sub>), exceeds +V<sub>REF</sub>. Next, if +V<sub>IN</sub> is gradually lowered, Vout will be inverted to the low level once again when the value of the noninverting input, (Vout V<sub>IN</sub>)*R1/(R<sub>1</sub> + R<sub>2</sub>), becomes lower than V<sub>REF</sub>. With the circuit constants shown in figure 7, assuming V<sub>CC</sub> = 15V and +V<sub>REF</sub> = 6V, the following formula can be derived, i.e.   +V<sub>IN</sub>*10M/(5.1M + 10M) > 6V, and Vout will invert from low to high when +V<sub>IN</sub> is > 9.06V.
   (Vout-VIN)*R1/(R1+R2)+VIN<6V
   (Assuming Vout = 15V)
   When +VIN is lowered, the output will invert from high to low when +V<sub>IN</sub> < 1.41V. Therefore this circuit has a hysteresis of 7.65V. Figure 8 shows the input characteristics
`Inverting Comparator (with Hysteresis)
In this circuit, the output Vout inverts from high to low when +V_IN > (V_CC + Vout)/3. Similarly, the output Vout inverts from low to high when +V_IN < V_CC/3. With the circuit constants shown in figure 9, assuming V_CC = 15V and Vout = 15V, this circuit will have a 5V hysteresis. Figure 10 shows the I/O characteristics for the circuit in figure 9
` Zero-Cross Detector (Single-Voltage Power Supply)
    In this circuit, the noninverting input will essentially beheld at the potential determined by dividing V_CC with 100k and 10k resistors. When V_IN is 0V or higher, the output will be low, and when V_IN is negative, Vout will invert to the high level. (See figure 11.)