Head driver

Claim 2

A head driver for driving a coil head for recording a signal responsive to a current flowing through the coil head in a magnetic recording medium, comprising: first and second source terminals for supplying first and second potentials, respectively; a capacitor having first and second ends, said first end being connected to said first source terminal; a control terminal for receiving a control signal having first and second levels for switching charging and discharging of said capacitor; a charging and discharging circuit provided between said first and second source terminals, having an input connected to said control terminal and an output connected to said second end of said capacitor, for charging said capacitor in response to said first level of said control signal and discharging said capacitor in response to said second level of said control signal; a voltage-current conversion circuit connected to said second end of said capacitor for converting a charging voltage of said capacitor to output a first current responsive to a level of the charging voltage; and a first current supply circuit connected with said coil head and said voltage-current conversion circuit for supplying said first current output from said voltage-current conversion circuit to said coil head.

Claim 3

A head driver in accordance with claim 1, wherein said charging and discharging circuit includes input means connected to said control terminal, said input means comprising a reference voltage source for supplying a reference voltage of a level between said first and second levels of said control signals, and a comparator having first and second inputs connected to said control terminal and said reference voltage source, respectively, and an output, for outputting first and second signals in response to said first and second levels of said control signal, respectively.

Claim 4

A head driver in accordance with claim 2, wherein said charging and discharging circuit further includes a charging circuit provided between said second source terminal and said second end of said capacitor and connected to said output of said comparator, for charging said capacitor in response to said first signal, and a discharging circuit provided between said first source terminal and said second end of said capacitor and connected to said output of said comparator, for discharging said capacitor in response to said second signal.

Claim 5

A head driver in accordance with claim 1, wherein said voltage-current conversion circuit comprises an aperational amplifier having first and second inputs and an output, said first input being connected to said second end of said capacitor, a first transistor having a first electrode through which said first current is output, a second electrode connected to said second input of said operational amplifier and a control electrode connected to said output of said operational amplifier, and a resistor connected between said second electrode of said first transistor and said first source terminal.

Claim 6

A head driver in accordance with claim 4, wherein said first current supply circuit comprises a first current mirror circuit connected to said first electrode of said first transistor, for supplying a second current responsive to said first current output through said first electrode of said first transistor, an input terminal for receiving an input signal for changing a direction of said current flowing through said coil head, and a second current supply circuit connected to said first current mirror circuit and said input terminal, for supplying a third current responsive to said second current to said coil head in a direction responsive to said input signal.

Claim 7

A head driver in accordance with claim 3, wherein said charging circuit includes a second current mirror circuit provided between said second source terminal and said second end of said capacitor, and coupled to said output of said comparator, for charging said capacitor in response to said first signal.

Claim 8

A head driver in accordance with claim 6, wherein said charging circuit further includes a third current mirror circuit provided between said first and second source terminals and connected to said output of said comparator and said second current mirror circuit, which is activated in response to said output of said comparator to activate said second current mirror circuit.

Claim 9

A head driver in accordance with claim 3, wherein said discharging circuit includes a fourth current mirror circuit provided between said first source terminal and said second end of said capacitor, for discharging said capacitor in response to said second signal.

Claim 10

A head driver in accordance with claim 8, wherein said discharging circuit further includes a second transistor having first, second and control electrodes connected to said fourth current mirror circuit, said first source terminal and said output of said comparator, respectively, for activating said fourth current mirror circuit in response to said second signal.

Claim 11

A head driver in accordance with claim 5, wherein said coil head has first and second ends, said input singal has first and second levels, and said second current supply circuit comprises a third transistor having first and second electrodes connected to said second source terminal and said first end of said coil head, respectively, and a control electrode coupled to said input terminal, which is turned on in response to said first level of said input signal, a fourth transistor having first and second electrodes connected to said second source terminal and said second end of said coil head, respectively, and a control electrode coupled to said input terminal, which is turned on in response to said second level of said input signal, a fifth current mirror circuit provided between said first end of said coil head and said first source terminal and coupled to said first current mirror circuit and said input terminal, which is activated in response to said second level of said input signal to supply said third current in a direction from said second end to said first end of said coil head, a sixth current mirror circuit provided between said second end of said coil head and said first source terminal and coupled to said first current mirror circuit and said input terminal, which is activated in response to said first level of said input signal to supply said third current in a direction from said first end to said second end of said coil head.

Claim 12

A head driver in accordance with claim 10, wherein said second current supply circuit further comprises an inverter having an input connected to said input terminal and an output connected to said control electrode of said third transistor and said sixth current mirror circuit.

Claim 13

A head driver in accordance with claim 10, wherein said first current mirror circuit comprises a fifth transistor having first and second electrodes connected to said fifth current mirror circuit and said second source terminal, respectively, and a control electrode, a sixth transistor having first and second electrodes connected to said sixth current mirror circuit and said second source terminal, respectively, and a control electrode connected to said control electrode of said fifth transistor, a seventh transistor having first and second electrodes connected to said first electrode of said first transistor and said second source terminal, respectively, and a control electrode connected to said control electrode of said fifth transistor, and an eighth transistor having first and second electrodes connected to said first source terminal and said control electrode of said seventh transistor, respectively, and a control electrode connected to said first electrode of said seventh transistor.

Claim 14

A head driver in accordance with claim 12, wherein said fifth current mirror circuit comprises a ninth transistor having first and second electrodes connected to said first end of said coil head and said first source terminal, respectively, and a control electrode coupled to said input terminal, and a first diode connected across said control electrode of said ninth transistor and said first source terminal, said sixth current mirror circuit comprising a tenth transistor having first and second electrodes connected to said second end of said coil head and said first source terminal, respectively, and a control electrode coupled to said input terminal, and a second diode connected across said control electrode of said tenth transistor and said first source terminal.

Claim 15

A head driver in accordance with claim 7, wherein said second current mirror circuit comprises a eleventh transistor having a first electrode, a second electrode connected to said second source terminal and a control electrode, a twelfth transistor having first and second electrodes connected to said second end of said capacitor and said second source terminal, respectively, and a control electrode connected to said control electrode of said eleventh transistor, and a thirteenth transistor having first, second and control electrodes connected to said first source terminal, said control electrode of said eleventh transistor and said first electrode of said eleventh transistor, said third current mirror circuit comprising a fourteenth transistor having first and second electrodes connected to said first electrode of said eleventh transistor and said first source terminal, respectively, and a control electrode coupled to said second source terminal and said output of said comparator, and a third diode connected across said control electrode of said fourteenth transistor and said first source terminal.

Claim 16

A head driver in accordance with claim 9, wherein said fourth current mirror circuit comprises a fifteenth transistor having first and second electrodes connected to said second end of said capacitor and said first source terminal, respectively, and a control electrode coupled to said second source terminal and said first electrode of said second transistor, and a fourth diode connected across said control electrode of said fifteenth transistor and said first source terminal.