Features, Applications The is a monostable multivibrator featuring both positive and negative edge triggering with complementary outputs. An internal 2k timing resistor is provided for design convenience minimizing component count and layout problems. A high immunity to VCC noise of typically 1. To obtain optimum and trouble free operation please read operating rules and one-shot application notes carefully and observe recommendations. Once triggered the output pulse width is independent of further transitions of the inputs and is function of the timing components.
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The number of frequency ranges can be increased by using a rotary switch SA1 with more than four positions, and by adding some additional RC components. The device can measure sinusoidal wave and square wave input signals. The pulse width produced by the monostable multivibrator depends on the values of capacitors C C5 and trimming potentiometers R The pulse frequency depends on the input frequency.
The pulse voltage is proportional to the input frequency, through the diode VD5 this voltage charges the capacitor C1. The ammeter PA1 indicates the voltage across the capacitor C1. How to calibrate this frequency meter? A quartz crystal oscillator circuit that can generates kHz signal with a 3-stage decade counter can be used as a reference frequency source see the Figure 2.
Turn the rotary switch S1 of the frequency meter to the range of Hz and connect the device to the reference signal source of Hz. Adjust the trimming potentiometer R3 to move the needle of ammeter PA1 to the maximum value on the scale. Do the same operation for all ranges. Reference oscillator circuit diagram This device uses the ammeter with full-scale deflection of 0. By the way, the ammeter PA1 can be replaced with a digital multimeter. Diodes VD VD4 protects the integrated circuit from overloading.
Instead of , the SN or DM can be used. George Kuzev, "Radio Televizia Elektronika" 11,
PDF 74121 Datasheet ( Hoja de datos )
Reproduction of information in TI data datasneet or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. TI has discontinued the production of the device. Datasheets search archive of electronic components datasheets Product device recommended for new datashfet. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. Not recommended for new designs. TI assumes no liability for applications assistance or customer product design.
Frequency meter with 74121 monostable multivibrator