Send a Single pulse "On"; Channel remains on until device's power is cut. Prefer op-amp solution
Here is positive-feedback opamp method; the 2 diodes are LOW_ACTIVE; you may want a rail-rail vin-vout opamp; scale up the resistors equally; the resistors may set your standby or latched-on current draw, so make them of high value.







simulate this circuit &ndash; Schematic created using CircuitLab