Schmitt trigger circuit

Claim 2

A Schmitt trigger circuit comprising: maximum voltage detecting means (12) for detecting and retaining a maximum voltage of an input signal (Vin); minimum voltage detecting means (13) for detecting and retaining a minimum voltage of said input signal (Vin); and threshold voltage generating means (20) for receiving said detected maximum and minimum voltages and generating threshold voltages.

Claim 3

The Schmitt trigger circuit according to claim 1, characterized in that said threshold voltage generating means (20) includes a resistor (16, 17, 18, 19).

Claim 4

The Schmitt trigger circuit according to claim 1, characterized in that said maximum voltage detecting means comprises: a reference voltage source (VB) connected to an input node (34) receiving said input signal (Vin); a power source (Vcc); a bipolar transistor (31) having a base connected to said input node (34) receiving said input signal (Vin) and to said reference voltage source (VB), and a collector connected to said power source (Vcc); a constant current source (33) connected between an emitter of said bipolar transistor (31) and a circuit ground; and a capacitor (32) connected between the emitter of the bipolar transistor (31) and a circuit ground.

Claim 5

The Schmitt trigger circuit according to claim 1, characterized in that said maximum voltage detecting means comprises: a reference voltage source (VB) connected to an input node (34) receiving said input signal (Vin); a power source (Vcc); a bipolar transistor (31) having a base connected to said input node (34) receiving said input signal (Vin) and to said reference voltage source (VB), and a collector connected to said power source (Vcc); a resistor (33A) connected between an emitter of said bipolar transistor (31) and a circuit ground; and a capacitor (32) connected between the emitter of the bipolar transistor (31) and a circuit ground.

Claim 6

The Schmitt trigger circuit according to claim 1, characterized in that said maximum voltage detecting means comprises: a reference voltage source (VB) connected to an input node (34) receiving said input signal (Vin); a power source (Vcc); a field-effect transistor (FET) (31B) having a gate connected to said input node (34) receiving said input signal (Vin) and to said reference voltage source (VB), and a drain connected to said power source (Vcc); a constant current source (33) connected between a source of said FET (31B) and a circuit ground; and a capacitor (32) connected between the source of said FET (31B) and a circuit ground.

Claim 7

The Schmitt trigger circuit according to claim 1, characterized in that said maximum voltage detecting means comprises: a reference voltage source (VB) connected to an input node (34) receiving said input signal (Vin); a power source (Vcc); a bipolar transistor (31) having a base connected to said input node (34) receiving said input signal (Vin) and to connected to said reference voltage source (VB), and a collector connected to said power source (Vcc); a constant current source (33) connected between an emitter of said bipolar transistor (31) and a circuit ground; and a capacitor (32C) connected between the emitter of the bipolar transistor (31) and said power source (Vcc).

Claim 8

The Schmitt trigger circuit according to claim 1, characterized in that said minimum voltage detecting means (13) comprises: a reference voltage source (VB) connected to an input node receiving said input signal (Vin); a power source (Vcc); a constant current source (41) connected to said power source (Vcc); a bipolar transistor (43) having a base connected to said input node (44) receiving said input signal (Vin) and to said reference voltage source (VB), and an emitter connected to said constant current source (41), and a collector connected to a circuit ground; and a capacitor (42) connected between the emitter of the bipolar transistor (43) and a circuit ground.

Claim 9

The Schmitt trigger circuit according to claim 1, characterized in that said minimum voltage detecting means (13) comprises: a reference voltage source (VB) connected to an input node (44) receiving said input signal (Vin); a power source (Vcc); a resistor (41A) connected to said power source (Vcc); a bipolar transistor (43) having a base connected to said input node (44) receiving said input signal (Vin) and to said reference voltage source (VB), and an emitter connected to said resistor (41A), and a collector connected to a circuit ground; and a capacitor (42) connected between the emitter of the bipolar transistor (43) and a circuit ground.

Claim 10

The Schmitt trigger circuit according to claim 1, characterized in that said minimum voltage detecting means (13) comprises: a reference voltage source (VB) connected to an input node (44) receiving said input signal (Vin); a power source (Vcc); a constant current source (41) connected to said power source (Vcc); a field effect transistor (FET) (43B) having a gate connected to said input node (44) receiving said input signal (Vin) and to said reference voltage source (VB), and a source connected to said constant current source (41), and a drain connected to a circuit ground; and a capacitor (42) connected between the source of said FET (43B) and a circuit ground.

Claim 11

The Schmitt trigger circuit according to claim 1, characterized in that said minimum voltage detecting means (13) comprises: a reference voltage source (VB) connected to an input node (44) receiving said input signal (Vin); a power source (Vcc); a constant current source (41) connected to said power source (Vcc); a bipolar transistor (43) having a base connected to said input node (44) receiving said input signal (Vin) and to said reference voltage source (VB), and an emitter connected to said constant current source (41), and a collector connected to a circuit ground; and a capacitor (42C) connected between the emitter of the bipolar transistor (43) and said power source (Vcc).