Transimpedance circuit

Patent metadata

Field	Value
Publication number	US-2016268975-A1
Application number	US-201514819186-A
Country	US
Kind code	A1
Filing date	Aug 5, 2015
Priority date	Mar 9, 2015
Publication date	Sep 15, 2016
Grant date	—

Abstract

According to one embodiment, a transimpedance circuit includes: a transimpedance amplifier that converts a current signal into a voltage signal, a reference voltage generating circuit that generates a reference voltage signal, and a comparator that generates a pulse signal corresponding to the current signal in accordance with a voltage level of the voltage signal and a voltage level of the reference voltage signal. The transimpedance amplifier includes a first transistor that amplifies the current signal, a voltage converter that converts the current signal into a voltage signal, and a bypass circuit that allows the current signal to be bypassed when the current signal which flows through a control terminal of the first transistor exceeds a predetermined value.

First claim

What is claimed is:

1 . A transimpedance circuit, comprising:
a transimpedance amplifier configured to convert a current signal into a voltage signal; a reference voltage generating circuit configured to generate a reference voltage signal; and a comparator configured to generate a pulse signal corresponding to the current signal in accordance with the voltage signal and the reference voltage signal, wherein the transimpedance amplifier includes: a first transistor configured to amplify the current signal; a voltage converter configured to convert the current signal into the voltage signal; and a bypass circuit configured such that the current signal bypasses the first transistor circuit when a level of the current signal at a control terminal of the first transistor exceeds a predetermined value.

2 . The transimpedance circuit according to claim 1 , wherein the bypass circuit includes a second transistor that is connected as a diode.

3 . The transimpedance circuit according to claim 2 , wherein the bypass circuit includes a resistance element that is connected in series with the second transistor.

4 . The transimpedance circuit according to claim 2 , wherein the first transistor and the second transistor are bipolar transistors.

5 . The transimpedance circuit according to claim 2 , wherein
the first transistor and the second transistor are MOS transistors, and a threshold voltage of the second transistor is lower than a threshold voltage of the first transistor.

6 . The transimpedance circuit according to claim 1 , wherein the bypass circuit includes a diode having a forward voltage that is less than 0.6 V.

7 . The transimpedance circuit according to claim 6 , wherein the diode is a Schottky barrier diode.

8 . The transimpedance circuit according to claim 1 , further comprising:
a light receiving element configured to output the current signal in correspondence with an optical signal incident thereon, wherein the bypass circuit is connected to an anode of the light receiving element.

9 . The transimpedance circuit according to claim 1 , wherein the first transistor is a bipolar transistor.

10 . The transimpedance circuit according to claim 1 , wherein the first transistor is a MOS transistor.

11 . A transimpedance circuit, comprising:
a first transistor connected between a first voltage terminal and a second voltage terminal and having a control electrode connected to a current signal input node; a second transistor connected between a current source and the second voltage terminal and having a control electrode connected to a first electrode of the first transistor; a third transistor connected between the first voltage terminal and a voltage signal node and having a control electrode connected to a second electrode of the second transistor; a voltage conversion circuit connected between the current signal input node and the voltage signal output node; and a bypass circuit connected between the current signal input node and the control electrode of the third transistor, the bypass circuit comprising a diode and configured to provide a conductance pathway between the current signal input node and the control electrode of the third transistor when a level of a current signal at the current signal input node exceeds a predetermined value.

12 . The transimpedance circuit according to claim 11 , wherein the diode is a diode-connected transistor.

13 . The transimpedance circuit according to claim 12 , wherein the diode-connected transistor is a metal-oxide-semiconductor field effect transistor.

14 . The transimpedance circuit according to claim 11 , wherein
the bypass circuit further comprises a resistor connected in series with the diode, and the diode is a diode-connected bipolar transistor.

15 . The transimpedance circuit according to claim 11 , further comprising:
a fourth transistor connected between the control electrode of the third transistor and the second electrode of the second transistor, the fourth transistor being a diode-connected transistor.

16 . The transimpedance circuit according to claim 11 , further comprising:
an inverting amplifier connected between the voltage signal output node and a second voltage signal output node and configured to output an inverted voltage signal corresponding to a current signal received at the current signal input node.

17 . The transimpedance circuit according to claim 11 , wherein the first, second, and third transistor are bipolar transistors.

18 . The transimpedance circuit according to claim 11 , wherein the first, second, and third transistors are metal-oxide-semiconductor field effect transistors.

19 . A transimpedance amplifier, comprising:
an initial-stage transistor circuit having a current signal input node at which a current signal is supplied and a control signal output node at which a control signal corresponding to the current signal is output; a voltage converter circuit connected between the current signal input node circuit and a voltage signal output node; and a bypass circuit connected between the current signal input node and the control signal output node and configured to conduct when a level of the current signal exceeds a predetermined value and to not conduct when the level is at or below the predetermined value.

20 . The transimpedance amplifier according to claim 19 , wherein the initial-stage transistor circuit comprises a pair of transistors in a Darlington configuration.

Assignees

• Toshiba Kk

Inventors

• Tsunetsugu Yukio

Classifications

• H03F3/082

  with FET's (H03F3/085 takes precedence) · CPC title

• H03F2200/78

  A comparator being used in a controlling circuit of an amplifier · CPC title

• H03F3/3435

  using Darlington amplifiers · CPC title

• H03F1/3205 Primary

  in field-effect transistor amplifiers · CPC title

• H03F3/08

  controlled by light · CPC title