1. Field of the Invention
The present invention relates to a variable drive current driver circuit.
2. Description of the Prior Art
According to the conventional standards, such as IEEE 1394 standards, a drive current of a signal transmitted between electronic devices, such as personal computers, video movies, or mini-disc players, connected mutually via a cable or the like is determined so as to become either of two kinds. When a certain electronic device is connected to another electronic device via a cable, the former have the latter notify the former of the standard of a signal that can be received by the latter, and the former transmits data with a drive current determined on the basis of this notification.
In other words, if a control signal of “1” is inputted to the standard A driver circuit and the standard B driver circuit, then the standard A driver circuit is enabled and the standard B driver circuit is disabled. If a control signal of “0” is inputted to the standard A driver circuit and the standard B driver circuit, then the standard A driver circuit is disabled and the standard B driver circuit is enabled.
In the conventional technique, however, it is necessary to prepare as many driver circuits as the number of kinds of the driver current defined by the standard. As a result, the circuit scale becomes large as the number of kinds of the drive current increases, especially in an electronic device, where transmission and reception of a plurality of data are performed using one physical layer LSI, it is especially desired to prevent the circuit scale from becoming large.
Therefore, the object of the present invention is to provide a variable drive current driver circuit having a small scale.
According to the first aspect of the present invention, there is provided a variable drive current driver circuit, comprising: a pair of push-pull circuits for driving a load circuit complementarily; a first current source circuit for having a bias current flow into the pair of push pull circuits; and a control circuit for varying both the bias current flowed by the first current source circuit and the bias current flowed by the second current source circuit according to a control signal.
In the variable drive current driver circuit, the first current source circuit comprises a current mirror circuit, and the control circuit controls an input current of the current mirror circuit according to the control signal.
In the variable drive current driver circuit, the control circuit may control the input current by controlling a control terminal voltage of a transistor for flowing the input current.
In the variable drive current driver circuit, the control of the control terminal voltage may be performed by changing, by a transistor which turns on or off according to the control signal, a magnitude of a load which flows through the output.
In the variable drive current driver circuit, the second current source circuit may comprise a transistor, and the control circuit may control a control terminal voltage of the transistor according to the control signal.
In the variable drive current driver circuit, the control of the second current source circuit may be performed by changing, by a transistor which turns on or off according to the control signal, a magnitude of a load which flows through the output.
According to a second aspect of the present invention, there is provided a variable drive current driver circuit, comprising: a pair of push-pull circuits for driving a load circuit complementarily; a first current source circuit for having a first bias current flow into the pair of push-pull circuits; a second current source circuit for having the first bias current flow out of the pair of push-pull circuits; a third current source circuit capable of having a second bias current flow into the pair of push-pull circuits; a fourth current source circuit capable of having the second bias current flow out of the pair of push-pull circuits; and a control circuit for varying both the second bias current flowed by the third current source circuit and the second bias current flowed by the fourth current source circuit according to a control signal.
In the variable drive current driver circuit, the control circuit mayhave the third current source circuit have the second bias current flow nor not flow into the pair of push-pull circuit, and the control circuit may have the fourth current source circuit have the second bias current flow or not flow out of the push-pull circuit.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Each of the instruction sections 11 and 21 is controlled by a CPU, which operates according to software and which is not illustrated. The control circuits 14 and 24 are incorporated in the LSIs 12 and 22 together with the variable drive current driver circuits 13 and 23, respectively.
With reference to
By the way, transistors PMOS 13 and NMOS 17 form a first push-pull circuit, whereas transistors PMOS 14 and NMOS 18 form a second push-pull circuit. Since a signal inputted to gates of the transistors PMOS 13 and NMOS 17 is complementary to a signal inputted to gates of the transistors PMOS 14 and NMOS 18, the first push-pull circuit and the second push-pull circuit complementarily drive the resistors R11 and R12 serving as a load circuit.
In accordance with the present invention, transistors NMOS 13 and NMOS 14 and a control signal input terminal are further added. The logic values of a control corresponds to CMOS levels. According to the logic value, the value of the drive current changes. In a case where the logic value of the control signal is “1,” a current Ib flows and a voltage Va becomes Va1. On the other hand, in a case where the logic value of the control signal is “0,” the current Ib does not flow and the voltage Va becomes Va2, wherein Va2>Va1. The currents Ic, Id1 and Id2 when the logic value of the control signal is “0” are larger than those when the logic value of the control signal is “1”, respectively. As a result, the control signal can generate two different drive current(s).
Comparing
Like the variable drive current driver circuit according to the first embodiment, the variable drive current driver circuit according to the second embodiment has two kinds of drive current controlled by the control signal.
Comparing
It is a matter of course that, like the circuit of the third embodiment, the variable drive current driver circuit according to the second embodiment can be expanded to enable the circuit to drive its load with a plurality of drive currents. To expand the circuit of
Number | Date | Country | Kind |
---|---|---|---|
2000-167798 | Jun 2000 | JP | national |
This application is a Divisional of U.S. application Ser. No. 09/874,737, filed Jun. 5, 2001 now U.S. Pat. No. 6,646,482.
Number | Name | Date | Kind |
---|---|---|---|
5450026 | Morano | Sep 1995 | A |
5898326 | Okayasu | Apr 1999 | A |
5949253 | Bridgewater, Jr. | Sep 1999 | A |
5977796 | Gabara | Nov 1999 | A |
6111431 | Estrada | Aug 2000 | A |
6194949 | Hogeboom | Feb 2001 | B1 |
6281715 | DeClue et al. | Aug 2001 | B1 |
6292028 | Tomita | Sep 2001 | B1 |
6313662 | Ide | Nov 2001 | B1 |
6329843 | Hirata et al. | Dec 2001 | B1 |
Number | Date | Country |
---|---|---|
63282868 | Nov 1988 | JP |
09214314 | Aug 1997 | JP |
10270992 | Oct 1998 | JP |
10326489 | Dec 1998 | JP |
11-085343 | Mar 1999 | JP |
2000-353035 | Dec 2000 | JP |
Number | Date | Country | |
---|---|---|---|
20040036512 A1 | Feb 2004 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 09874737 | Jun 2001 | US |
Child | 10647582 | US |