公开(公告)号：DE69421923T2

公开(公告)日：2000-05-18

申请号：DE69421923

申请日：1994-09-30

Applicant: ST MICROELECTRONICS SRL

Inventor： DEGLI ANTONI GIOVANNI ,  BISIANI ROBERTO ,  MURARI BRUNO

IPC: B60R25/04

公开(公告)号：DE69032087T2

公开(公告)日：1998-10-08

申请号：DE69032087

申请日：1990-12-13

Applicant: ST MICROELECTRONICS SRL

Inventor： MURARI BRUNO ,  ROSSI DOMENICO ,  SAVINO PIERANTONIO

IPC: G11B5/02 ,  H03F3/181 ,  H03F3/343 ,  G11B5/027 ,  H03F3/45

Abstract: A low-noise preamplifier stage, in particular for magnetic heads, which comprises a differential circuit (T5,T6) and a single-transistor output stage (T2). The differential stage has an intrinsic offset voltage, is ground-connectable and can be directly coupled to the magnetic head (L) , the two transistors forming the differential circuit (T5,T6) having different bias currents in order to reduce the input equivalent noise. The base terminal of the first transistor (T5) of the differential circuit defines an input (IN) of the stage which can be connected directly to a terminal of the magnetic head (L); the other terminal of the head can be connected directly to the ground. The base terminal of the other transistor (T6) of the differential circuit (T5,T6) is connected to the intermediate point of a pair of resistors (R1,R2) which are mutually connected in series between the single transistor of the output stage (T2) and a line at reference voltage. In this manner the differential stage (T5,T6) biases the output with its offset voltage without requiring additional components for this purpose.