# US 2013/0278335 A1 · High Speed, Low Power Write Current Switching Scheme for HDD Preamplifier > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0278335 A1 - Document ID: US20130278335A1 - Status: Published application - Kind: A1 - Application number: 13/570,429 - Filed: 2012-08-09 - Published: 2013-10-24 - Earliest claimed: 2012-04-20 - Assignees: Texas Instruments Incorporated - Inventors: Jeremy Robert Kuehlwein - Web page: https://patentgrep.com/patent/US20130278335A1 ## CPC - H03F 3/45085: {Long tailed pairs (H03F3/45112, H03F3/45139 take precedence)} - G11B 5/022: {H-Bridge head driver circuit, the "H" configuration allowing to inverse the current direction in the head} - H03F 2203/45654: the LC comprising one or more extra diodes not belonging to mirrors - H03F: AMPLIFIERS - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract A hard drive write preamplifier includes a first differential pair of PNP BJTs having a first PNP BJT and a second PNP BJT; a first tail current source coupled into emitter of the PNP BJTs of the first differential pair; a second differential pair of NPN BJTs having a first NPN BJT and a second NPN BJT; a second tail current source coupled into the emitters of the NPN BJTs of the second differential pair; wherein a collector of each of the PNP BJTs of the first differential pair are coupled to a corresponding collector the NPN BJTs of the second differential pair; a first shift up PNP BJT having emitter coupled to the collector of a first PNP BJT of the first differential pair; a second shift up PNP BJT having an emitter coupled to the collector of the second PNP BJT of the first differential pair. ## Claims ### Claim 1 An apparatus, comprising: a first differential pair of PNP BJTs having a first PNP BJT and a second PNP BJT; a first tail current source coupled into the emitter of the PNP BJTs of the first differential pair; a second differential pair of NPN BJTs having a first NPN BJT and a second NPN BJT; a second tail current source coupled into the emitters of the NPN BJTs of the second differential pair; wherein a collector of each of the PNP BJTs of the first differential pair are coupled to a corresponding collector the NPN BJTs of the second differential pair; a first shift up PNP BJT having an emitter coupled to the collector of a first PNP BJT of the first differential pair, a second shift up PNP BJT having an emitter coupled to the collector of the second PNP BJT of the first differential pair; a first shift down NPN BJT having an emitter coupled to the collector of the first PNP BJT of the second differential pair; a second shift up BJT having an emitter coupled to the collector of a second PNP BJT of the second differential pair; and a first and second amplifier coupled to the emitters of the a first shift up PNP BJT and the second shift up PNP BJT. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the first tail source and the second tail source are programmable. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein a collector of a first shift up PNP BJT is coupled to a first voltage source, and an emitter of a first shift on NPN BJT is coupled to a second voltage source. ### Claim 4 (depends on 1) The apparatus of claim 1, further comprising a first resistor coupled to an output of the first resistor, further comprising a first output resistor coupled to an output of the first output resistor, and at least a portion of a hard drive coupled between the first output resistor and the second output resistor. ### Claim 5 (depends on 1) The apparatus of claim 1, further comprising: a down shift transistor that has an emitter coupled to the base of the first up shift transistor, and an up shift transistor that has an emitter coupled to the base of the first down shift transistor. ### Claim 6 (depends on 1) The apparatus of claim 1, further comprising a first static current source and a second static current source, an output of both of which are coupled to the base of the down shift transistor and the up shift transistor, respectively. ### Claim 7 (depends on 1) The apparatus of claim 1, further comprising a first resistor and a second resistor coupled to an output of the first and second static current sources, and a first capacitor coupled in parallel to the first resistor, and a second capacitor coupled in parallel to the second resistor. ### Claim 8 An apparatus, comprising: a first differential pair of PNP BJTs having a first PNP BJT and a second PNP BJT; a first tail current source coupled into the emitter of the PNP BJTs of the first differential pair; a second differential pair of NPN BJTs having a first NPN BJT and a second NPN BJT; a second tail current source coupled into the emitters of the NPN BJTs of the second differential pair; wherein a collector of each of the PNP BJTs of the first differential pair are coupled to a corresponding collector the NPN BJTs of the second differential pair; a first shift up PNP BJT having an emitter coupled to the collector of a first PNP BJT of the first differential pair; a second shift up PNP BJT having an emitter coupled to the collector of the second PNP BJT of the first differential pair; a first shift down NPN BJT having an emitter coupled to the collector of the first PNP BJT of the second differential pair; a second shift up BJT having an emitter coupled to the collector of a second PNP BJT of the second differential pair; and a first and second amplifier coupled to the emitters of the a first shift up PNP BJT and the second shift up PNP BJT, a first static current source and a second static current source, an output of both of which are coupled to the base of the down shift transistor and the up shift transistor, respectively, and wherein the first static current source and the first tail current source share a node; and wherein the second static current source and the first tail current source share a node. ### Claim 9 (depends on 8) The circuit of claim 8, wherein the first tail source and the second tail source are programmable. ### Claim 10 (depends on 8) The apparatus of claim 8, wherein a collector of a first shift up PNP BJT is coupled to a first voltage source, and an emitter of a first shift on NPN BJT is coupled to a second voltage source. ### Claim 11 (depends on 8) The apparatus of claim 8, further comprising a first resistor coupled to an output of the first resistor, further comprising a first output resistor coupled to an output of the first output resistor, and at least a portion of a hard drive coupled between the first output resistor and the second output resistor. ### Claim 12 (depends on 8) The apparatus of claim 8, further comprising: a down shift transistor that has an emitter coupled to the base of the first up shift transistor, and an up shift transistor that has an emitter coupled to the base of the first down shift transistor. ### Claim 13 (depends on 8) The apparatus of claim 8, further comprising a first resistor and a second resistor coupled to an output of the first and second static current sources, and a first capacitor coupled in parallel to the first resistor, and a second capacitor coupled in parallel to the second resistor. ### Claim 14 An apparatus, comprising: a first differential pair of PNP BJTs having a first PNP BJT and a second PNP BJT; a first tail current source coupled into the emitter of the PNP BJTs of the first differential pair; a second differential pair of NPN BJTs having a first NPN BJT and a second NPN BJT; a second tail current source coupled into the emitters of the NPN BJTs of the second differential pair; wherein a collector of each of the PNP BJTs of the first differential pair are coupled to a corresponding collector the NPN BJTs of the second differential pair; a first shift up PNP BJT having an emitter coupled to the collector of a first PNP BJT of the first differential pair; a second shift up PNP BJT having an emitter coupled to the collector of the second PNP BJT of the first differential pair; a first shift down NPN BJT having an emitter coupled to the collector of the first PNP BJT of the second differential pair; a second shift up BJT having an emitter coupled to the collector of a second PNP BJT of the second differential pair; and a first and second amplifier coupled to the emitters of the a first shift up PNP BJT and the second shift up PNP BJT, a first static current source and a second static current source, an output of both of which are coupled to the base of the down shift transistor and the up shift transistor, respectively, and wherein the first static current source and the first tail current source share a node; wherein the second static current source and the first tail current source share a node; and a diode coupled to the emitter of the first downshift BJT and the base of the first upshift BJT. ### Claim 15 (depends on 14) The circuit of claim 14, further comprising a diode coupled to the collector of the first upshift BJT and the base of the first downshift BJT. ### Claim 16 (depends on 14) The circuit of claim 14, further comprising a diode coupled between an emitter of the first upshift PNP and the collector of the first PNP of the amplifier pair. ### Claim 17 (depends on 14) The circuit of claim 14, further comprising a diode coupled between an emitter of the first downshift NPNP and the collector of the first NPS of the amplifier pair. ### Claim 18 (depends on 14) The apparatus of claim 14, wherein the first tail source and the second tail source are programmable. ### Claim 19 (depends on 14) The apparatus of claim 14, wherein a collector of a first shift up PNP BJT is coupled to a first voltage source, and an emitter of a first shift on NPN BJT is coupled to a second voltage source. ### Claim 20 (depends on 14) The apparatus of claim 14, further comprising a first resistor coupled to an output of the first resistor, further comprising a first output resistor coupled to an output of the first output resistor, and at least a portion of a hard drive coupled between the first output resistor and the second output resistor.