Apparatus for providing pair of complementary outputs with first and subcircuits to convert non-complementary and complementary inputs to first and second pair of complementary output

摘要

A write driver, having a pair of inputs for receiving write data signals, includes a TTL buffer circuit connected to one input and a PECL buffer circuit connected to both inputs. A detector, responsive to a voltage at one of the inputs, selectively operates either the TTL buffer circuit or the PECL buffer circuit. The detector preferably comprises a comparator, a switching circuit, and two current mirrors. The comparator compares the voltage at one of the inputs to a reference voltage and outputs a signal controlling the switching circuit. The switching circuit enables one of the current mirrors, thereby enabling either the TTL or the PECL buffer circuit. In the preferred embodiment, a Schottky diode isolates the TTL buffer circuit from the PECL buffer circuit.