Circuits for linear conversion between voltages and currents

• US 5,126,685 A
• Filed: 08/19/1991
• Issued: 06/30/1992
• Est. Priority Date: 12/18/1990
• Status: Expired due to Term

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Wall, Michael F., Platt, John C., Mead, Carver A., Gribble, Glenn E.
• Primary Examiner(s): MOTTOLA, STEVEN J
• Application Number:
  US07/746,962
• Time in Patent Office: 316 Days
• Field of Search: 307/530, 330/85, 330/109, 330/277, 330/291
• US Class Current: 330/85
• CPC Class Codes: H03F 2203/30006 the push and the pull stages of the SEPP amplifier are both current mirrors
• CPC Class Codes: H03F 2203/30009 the push and pull stages of the SEPP amplifier are both cascode current mirrors
• CPC Class Codes: H03F 2203/30084 the pull circuit of the SEPP amplifier being a cascode circuit
• CPC Class Codes: H03F 2203/30117 the push circuit of the SEPP amplifier being a cascode circuit
• CPC Class Codes: H03F 3/3001 with field-effect transistors
• CPC Class Codes: H03F 3/3022 CMOS common source output SEPP amplifiers H03F3/3008 takes precedence

Abstract

A linear voltage-to-current converter (LVCC) circuit includes two transistors, one P-channel and one N-channel. The input voltage is applied to the gates of both transistors. The drains of the two transistors are connected. The source of the p-type transistor is connected to a first voltage rail, and the source of the N-channel is connected to a second voltage rail of lower voltage. The output is the difference between the current through the P-channel transistor and the N-channel transistor. A linear current-to-voltage converter (LCVC) circuit is similar to the LVCC circuit, except that the gates of the transistors are tied to the drains of the transistors. The input current is supplied to the drains, and the output voltage is the voltage of the drains.

Claims

1. A current sense amplifier, including:

a non-inverting amplifier having an input node and an output node;

a voltage-to-current converter circuit, having an input node connected to the output node of said amplifier and an output node connected to the input node of said amplifier;

a capacitor connected between said input node and said output node of said non-inverting amplifier;

wherein said voltage-to-current converter circuit includes a P-channel MOS transistor having its drain connected to the drain of an N-channel MOS transistor to form the output node of said voltage-to-current converter circuit, and having its gate connected to the gate of said N-channel MOS transistor to form the input node of said voltage-to-current converter circuit, the source of said P-channel MOS transistor connected to a first voltage rail and the source of said N-channel MOS transistor connected to a second voltage rail, more negative than said first voltage rail.

2. A current sense amplifier, including:

a non-inverting amplifier having an input node and an output node;

a voltage-to-current converter circuit, having an input node connected to the output node of said amplifier and an output node connected to the input node of said amplifier;

a capacitor connected between said input node and said output node of said non-inverting amplifier;

wherein said voltage-to-current circuit includes a P-channel MOS transistor having its drain connected to the drain of an N-channel MOS transistor to form the output node of said voltage-to-current converter circuit, and having its gate connected to the gate of said N-channel MOS transistor to form the input node of said voltage-to-current converter circuit, the source of said P-channel MOS transistor connected to at least one diode connected P-channel MOS transistor in series with a first voltage rail and the source of said N-channel MOS transistor connected to at least one diode connected N-channel MOS transistor in series with a second voltage rail, said second voltage rail being more negative than said first voltage rail.