Transistorized load control circuit

Claim 2

A load control circuit for operating a load circuit, comprising: an input terminal for receiving input control voltage conditions; a first source of potential; a second source of potential; a source of reference potential; a first transistor having base, collector, and emitter, the base being coupled to the input terminal and the collector being coupled to the first source of potential; a second transistor having base, collector, and emitter; a resistance connected in series with the emitter of the first transistor and the base of the second transistor; first diode means connected in series with the emitter of the first transistor and the emitter of the second transistor, said first diode means having a conducting state and a nonconducting state; second diode means coupled in series with the collector of the second transistor and the second source of potential, said second diode means having a conducting state and a nonconducting state; means for connecting a load circuit in series with the emitter of the second transistor and the source of reference potential; said second transistor being operable in a conducting state, said second diode means being operable in its conducting state, and said first diode means being operable in its nonconducting state in response to a first input control voltage condition at the input terminal, whereby current is supplied from the second source of potential to the load circuit via the conducting second diode means and the conducting second transistor; and said first transistor being operable in a conducting state, said first diode means being operable in its conducting state, and said second diode means being operable in its nonconducting state in response to a second input control voltage condition at the input terminal, whereby current is supplied from the first source of potential to the load circuit via the conducting first transistor and the conducting first diode means.

Claim 3

A load control circuit in accordance with claim 1 wherein: the first input control voltage condition forward biases the base-emitter junction of the second transistoR; and the second input control voltage condition forward biases the base-emitter junction of the first transistor, the first diode means, and the base-collector junction of the second transistor.

Claim 4

A load control circuit in accordance with claim 1 wherein: the first source of potential is a positive high-voltage source; the second source of potential is a positive low-voltage source; the source of reference potential provides a potential which is negative with respect to the low-voltage source; the first and second transistors are NPN-transistors; the first diode means comprises a pair of series-connected diodes, the anode of the first one of the pair of diodes being coupled to the emitter of the first transistor, the cathode of the first one of the pair of diodes being coupled to the anode of the second one of the pair of diodes, and the cathode of the second one of the pair of diodes being coupled to the emitter of the second transistor; and the second diode comprises a diode having its anode coupled to the second source of potential and its cathode coupled to the collector of the second transistor.

Claim 5

A load control circuit for operating a load circuit, comprising: an input terminal for receiving input control voltages; a high-voltage source; a low-voltage source; a source of reference potential; a first transistor having base, collector, and emitter, the base being connected directly to the input terminal and the collector being connected directly to the high-voltage source; a second transistor having base, collector, and emitter; a resistance connected in series with the emitter of the first transistor and the base of the second transistor; first and second diodes connected in series between the emitter of the first transistor and the emitter of the second transistor, said first and second diodes being poled for easy current flow between the emitter of the first transistor and the emitter of the second transistor; a third diode connected in series with the collector of the second transistor and the low-voltage source, said third diode being poled for easy current flow between the low-voltage source and the collector of the second transistor; means for connecting a load circuit in series with the emitter of the second transistor and reference potential; said resistance having a value selected such that for a control voltage at the input terminal having a value at least equal to the forward-bias base-emitter voltages of the first and second transistors- but less than the value of the low-voltage source, plus the value of the forward-bias base-emitter voltage of the first transistor, plus the value of the base-collector voltage of the second transistor, minus the value of the forward-bias voltage of the third diode-the second transistor and the third diode operate in their conducting states and the first and second diodes operate in their nonconducting states, whereby current is supplied from the low-voltage source to the load circuit via the conducting third diode and the conducting second transistor, and such that for a control voltage at the input terminal having a value equal to or greater than the value of the low-voltage source, plus the value of the forward-bias base-emitter voltage of the first transistor, plus the value of the base-collector voltage of the second transistor, minus the value of the forward-bias voltage of the third diode, the first transistor and the first and second diodes operate in their conducting states and the third diode operates in its nonconducting state, whereby current is supplied from the high-voltage source to the load circuit via the conducting first transistor and the conducting first and second diodes.

Claim 6

A load control circuit for operating a load circuit, comprising: an input terminal for receiving input control voltages; a high-voltage source; a low-voltage source; a source of reference potential; a first transistor having base, collector, and emitter, the base being connected directly to the input terminal and the collector being connected directly to the high-voltage source; a second transistor having base, collector, and emitter; a resistance connected in series with the emitter of the first transistor and the base of the second transistor; first and second diodes connected in series between the emitter of the first transistor and the emitter of the second transistor, said first and second diodes being poled for easy current flow between the emitter of the first transistor and the emitter of the second transistor; a third diode connected in series with the collector of the second transistor and the low-voltage source, said third diode being poled for easy current flow between the low-voltage source and the collector of the second transistor; means for connecting a load circuit in series with the emitter of the second transistor and reference potential; said resistance having a value selected such that for a control voltage at the input terminal having a value at least equal to the forward-bias base-emitter voltages of the first and second transistors- but less than the value of the low-voltage source, plus the value of the forward-bias base-emitter voltage of the first transistor, plus the value of the base-collector voltage of the second transistor, minus the value of the forward-bias voltage of the third diode-the second transistor and the third diode operate in their conducting states and the first and second diodes operate in their nonconducting states, whereby current is supplied from the low-voltage source to the load circuit via the conducting third diode and the conducting second transistor, and such that for a control voltage at the input terminal having a value equal to or greater than the value of the low-voltage source, plus the value of the forward-bias base-emitter voltage of the first transistor, plus the value of the base-collector voltage of the second transistor, minus the value of the forward-bias voltage of the third diode, the first transistor and the first and second diodes operate in their conducting states and the third diode operates in its nonconducting state, whereby current is supplied from the high-voltage source to the load circuit via the conducting first transistor and the conducting first and second diodes.

Claim 7

A load control circuit in accordance with claim 4 wherein: the high-voltage and low-voltage sources are positive voltage sources; the reference potential is ground potential; and the first and second trAnsistors are NPN-transistors.