Abstract: A monolithically integrated resistive attenuator is autobiased from an input bipolar signal the amplitude of which is higher than the integrated circuit voltage supplies. The resistive attenuator is arranged in a first pocket formed in an epitaxial layer, and is connected between the input bipolar signal and ground. An intermediate tap produces an output signal. A diode and capacitor are formed in a second pocket. The diode is connected between the input bipolar signals and the epitaxial layer while the capacitor is connected between the epitaxial layer and the isolation walls thereof. The positive half-periods of the input bipolar signal charges the capacitor, which in turn biases the epitaxial layers. The attenuator, therefore, can be monolithically integrated into a silicon chip and remain isolated for all values of the input bipolar signal.

Abstract: A circuit for receiving signals from a device connected through a line meeting the requirements of EIA RS232C Standard, comprising a differential amplifier (2) receiving an input signal the amplitude of which is divided by factor k through input network (1). The switching threshold of amplifier (2) is variable and has a first value to ensure switching on the positive slope edge of the input signal and a second value to ensure switching on the negative slope edge. This circuit comprises circuits for detecting the status of the connected device, including a level detector (3) and a decision circuit (4) which, according to the outputs of the receiver and level detector (5), generates a signal indicating the status of the connected device. Integrators (5, 6) are provided for preventing the status indicating signal from changing its level when the input signal goes through zero or receives short noise pulses.