555 Bistable Multivibrator
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NE555 wired as a bistable (set/reset latch): S1 sets the output high via TRIG, S2 clears it via RESET; THRESH is grounded so it never times out. An LED shows the state.
Parts
| Part | Count | Values and models |
|---|---|---|
| Resistor | 4 | 470, 10k |
| Voltage source | 3 | 5, PULSE(0 5 {tset} 10u 10u 0.5m 1), PULSE(0 5 {trst} 10u 10u 0.5m 1) |
| Voltage switch (S) | 2 | SW |
| NE555 | 1 | |
| Diode | 1 | LED_RED |
| Capacitor | 1 | 10n |
Picture
Simulation
This circuit is set up for a transient (time domain) analysis: .tran 0 10m 0 10u. Run it in your browser, change values and see the waveforms update.
SPICE netlist
* 555 Bistable Multivibrator - Main
.param tset=3m
.param trst=7m
X1 0 trig out rst n001 0 n002 vcc NE555
R1 out n003 470
D1 n003 0 LED_RED
R4 vcc n002 10k
V1 vcc 0 5
C1 n001 0 10n
R2 vcc trig 10k
S1 0 trig n004 0 SW
V2 n004 0 PULSE(0 5 {tset} 10u 10u 0.5m 1)
R3 vcc rst 10k
S2 0 rst n005 0 SW
V3 n005 0 PULSE(0 5 {trst} 10u 10u 0.5m 1)
.include NE555.sub
.model LED_RED D(Is=1e-18 N=1.8 Rs=10 Cjo=10p)
.model SW SW(Ron=0.1 Roff=10meg Vt=0.5 Vh=0)
.meas tran v_latched FIND V(out) AT=4.5m
.meas tran v_cleared FIND V(out) AT=9m
.tran 0 10m 0 10u
.end
