Current Switch Circuit
Original Publication Date: 1988-Nov-01
Included in the Prior Art Database: 2005-Feb-15
A write current switch provides a compact, fast, accurate and low-power method of switching a servo preamplifier module between read mode and write mode. In addition, the circuit is inherently safer than other configurations since the negative voltage required to write data is not present in the final product. Fig. 1 illustrates the use of the write current switch in a disk file servo preamplifier module. Switch 1 is used to switch from read circuitry, switch 2 to write circuitry, and switch 3 when current is pulled from IW. Fig. 2 describes the circuit operation. Connectors 8 and 3 are biased at 2.6 volts. When current is pulled out of connector IW, transistors Q3, Q2, and Q1 conduct, biasing node 15 at 1.8 volts and node 16 at 4.2 volts. Since node 47 is biased at 5.