Monostable Circuits

This circuit is activated when SW1 is pushed to ground the base of transistor Q2...

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In the monostable mode, the resistor can be replaced by aconstant current source to provide a linear ramp voltage..

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In this mode, the timer functions as a one shot. The external capacitor is initially held discharged by a transistor internal to the timer. Applying a negative trigger pulse to pin 2 sets the flip-flop, driving the output high, and releasing the short circuit across the external capacitor. The voltage across the capacitor increases with the time constant r ~ RAC to 213 V5, where the comparator resets the flip-flop and discharges the external capacitor. The output.....

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The output of a video amplifier is differentiated before being fed to a Schottky comparator. The propagation delay is reduced to typically 10ns. The output pulse width is set by the value of C, lOOpf giving a pulse of about 90ns duration. ..

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The 555 is a highly stable device for generating accurate time delays or oscillation. Aditional terminals are provided for triggering or resetting if desired. In the time delay (monostable) modeof operation the time is precisely controlled by one extrernal resistor and one capacitor. For stable operation as an oscillator, the free running frequency and the duty cycle are both accurately controlled with two external resistors and one capacitor...

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If you need a wide-range, resistor-programmable monostable multivibrator, you can program tbe circuit for pulse widths from 1 JlS to 10s-107:1 range. A high-to-low transition at tbe input causes IC1"s output to switch low, thereby turning off Q1 and Q2. With tbe latter transistor turned off, IC3"s output increases and tbe output ofIC2 begins to ramp toward tbe negative supply level at a rate determined by the 0.01-JlF capacitor and tbe programming resistor. ..

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A photocell circuit provides automatic threshold adjustment. Monostable action prevents undesired retriggering of the output. With only one op amp IC, the circuit offers: Automatic adjustment of its trigger level to accommodate various light sources, changes in ambient light and misalignments; A built-in monostable action to provide only a single output pulse during a preset time; Feedback action to raise the threshold level after triggering and to speed switching...

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A positive-going trigger pulse can be used to start the timing cycle with the circuit shown. In this design, trigger input pin 2 is biased to 6V (1/z Vvv) by divider Rl and R2. Control input pin 5 is biased to 8 V (213 Vvvl by the internal divider circuit. With no trigger voltage applied, point A is at 4 V (1/3 Vvv). To tum the timer on, the voltage at point A has to be greater than the 6 V present on pin 2. Positive 5-V trigger pulse V, applied to the control input.....

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The time constant of RAXC determines the period of the monostable multivibrator. ..

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The circuit illustrates the usefulness of the HA-5151 as a battery-powered monostable. In this circuit, the ratio is set to .632, which allows the time constant equation to be reduced to: T=R1*C1. D2 is used to force the output to a defined state by clamping the negative input at +0.6 V. Triggering is set by C1, R3, and D2. ..

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This circuit was designed to detect when a call is incoming in a cellular phone (even when the calling tone of the device is switched-off) by means of a flashing LED. The device must be placed a few centimeters from the cellular phone, so its sensor coil L1 can detect the field emitted by the phone receiver during an incoming call. The signal detected by the sensor coil is amplified by transistor Q1 and drives the monostable input pin of IC1. The IC`s output voltage is.....

This circuit will remove the transient spikes and contact bounces from a non-latching push button switch. Using a 555 timer as a monostable circuit, it is easy to build a good switch debouncer circuit. There are many circuits for SPDT debouncing, but not many for a normally open, push-to-make press button switch (PBS). The 555 monostable gives an output pulse of around 20 msec with component values shown...

A classic one-shot multivibrator using an op amp (Figure 1a) needs a relatively long-duration triggering pulse, even though the circuit is in theory a slope-triggered configuration. This limitation can be a problem when you want to use a "spare" op amp from a dual or quad package (LM324, LM358, LM6482, or LT1013, for example) triggered from fast logic circuitry. The op amp`s limited slew rate (SR) creates the problem...

The logic diagram of the CD4538BC Dual Precision Monostable is shown in the following schematic diagram. This IC such a dual, precision monostable multivibrator with independent trigger and controls, according to the datasheet. This CD4538BC IC features wide supply voltage range, wide pulse-width range, low standby current, high noise immunity and more...

The circuit in Figure 1 is a simple, low-cost voltage-to-time converter using the ubiquitous 555 timer chip. You can use the IC`s monostable multivibrator as a voltage-to-time converter by connecting the analog-voltage input to the charging resistor, R, instead of connecting R to VCC. With this modification, the timer chip`s output-timing cycle, tP, is proportional to the input voltage, VIN...

This circuit was designed to detect when a call is incoming in a cellular phone (even when the calling tone of the device is switched-off) by means of a flashing LED. The device must be placed a few centimeters from the cellular phone, so its sensor coil L1 can detect the field emitted by the phone receiver during an incoming call. The signal detected by the sensor coil is amplified by transistor Q1 and drives the monostable input pin of IC1. The IC`s output voltage is.....

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The circuits in Figure 1 have certain advantages over those in a previous Design Idea (Reference 1). The first-event detector with autoreset (Figure 1a) consists of N sets of monostable multivibrators, using 4001 logic circuits with LEDs attached. After any player (1 through N) presses a pushbutton, the corresponding monostable multivibrator switches on, and its associated LED lights...

The two circuits below illustrate using the 555 timer to close a relay for a predetermined amount of time by pressing a momentary N/O push button. The circuit on the left can be used for long time periods where the push button can be pressed and released before the end of the timing period. For shorter periods, a capacitor can be used to isolate the switch so that only the initial switch closure is seen by the timer input and the switch can remain closed for an unlimited.....

You can divide a large keypad or keyboard into sections of 12 keys each (Figure 1). Each section connects to a separate comparator circuit, which detects a keystroke and generates a trigger pulse using the monostable circuit of IC4, and you can add more sections in the same manner. Diodes D1, D2, and D3 couple and isolate the comparators` outputs to Pin 2 of IC4. Each keypad section connects the same selection of timing-resistor values to the monostable. Therefore, each.....

The easy way to clamp a signal to a given value is to use two zener diodes, connected back-to-back. This method has several disadvantages. The accuracy of the clamping depends on the tolerance of the zener diodes, and the clamping is not adjustable, except by changing diodes. The circuit in Figure 1 is a bipolar clamper with a range of ±1 to ±10V, with the clamping level a function of the input VCLAMP...