c25 Make CMOS constructions simple
|Logic gates for CMOS
g) NAND/NOR combination
Alternative way to make gates with diodes and
resistors for lower data rates.
Improved 1000Hz CMOS astable oscillator. It may also be used to measure time with a frequency counter set to count the number of pulses.
If a CD4001 is used instead of CD4011, the oscillator will be running when input is grounded.
The figure shows how 3x EXOR gates (CD4070 or 74C86) may be connected as 3x inverters for an astable oscillator. If a package with X-NOR gates like CD4077 was available, pins 2-3-16 are grounded instead.
It is sometimes practical to add som transistor logic to avoid using more than a minimum amount of cmos IC's.
A derivation circuit is suitable circuit to make with a transistor instead of using an extra CD4098, 74C221, CD4538 or other monostable IC.
The diode is needed in series with base or emitter when base-emitter breakdown voltage is lower than Vdd, so usually it is not needed.
Improved capacitance meter - one of the last experiments being tested by LA7MI - shown as I would have made it.
May use 556 or TLC556 , and CD4077 CMOS gates