ALL NPN-TRANSISTOR PTAT CURRENT SOURCE

• US 20090295465A1
• Filed: 11/08/2005
• Published: 12/03/2009
• Est. Priority Date: 11/11/2004
• Status: Active Grant

• Current Assignee: ST-Ericcson SA (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Sanduleanu, Mihai A .T., Blanken, Pieter G., Tripodi, Lorenzo
• Granted Patent: US 7,952,421 B2
• Time in Patent Office: Days
• US Class Current: 327/538
• CPC Class Codes: G05F 3/262 using field-effect transistors only

Abstract

The present invention relates to an improved PTAT current source and a respective method for generating a PTAT current. Opportune collector currents are generated and forced in two transistors exploiting the logarithmic relation between the base-emitter voltage and the collector current of a transistor. A resistor senses a voltage difference between the base-emitter voltages of the two transistors, which can have either the same or different areas. A fraction of the current flowing through the resistor is forced into a transistor collector and mirrored by an output transistor for providing an output current. By this principle an all npn-transistor PTAT current source can be provided that does not need pup transistors as in conventional PTAT current sources. The invention is generally applicable to a variety of different types of integrated circuits needing a PTAT current reference, especially in modern advanced technologies as InP and GaAs where p-type devices are not available. For example, the PTAT current source circuit of the invention can be used in radio frequency power amplifiers, in radio frequency tag circuits, in a satellite microwave front-end.

Claims

1. A circuit for generating a current being proportional to absolute temperature, said circuit comprising:

a first current path including a first resistive element and first transistor means coupled at a first node and a second current path in parallel with the first current path including a second resistive element and a second transistor means coupled at a second node;

a PTAT current path in parallel with the first and second current paths including a first current source configured to be controlled by a signal from said first node, a second current source configured to be controlled by a signal from said second node, and a current sensing element inter-coupled between said first current source and said second current source at a third node and a fourth node, respectively; and

a control terminal of said first transistor means coupled to said fourth node and a control terminal of said second transistor means coupled to said third node.

2. Circuit according to claim 1, further comprising a third current path including a third current source configured to be controlled by said signal of said second node and to emboss a reference current into current mirror means.

3. Circuit according to claim 2, wherein said second current source is a mirror current source of said current mirror means.

4. Circuit according to claim 1, further comprising a fourth current path including a fourth current source configured such that a current of said fourth current source is proportional to a current of said second current source.

5. Circuit according to claim 4, wherein said fourth current path further comprises a fifth current source configured to be controlled by said signal from said first node.

6. Circuit according to claim 1, further comprising a fifth current path including a third resistive element and third transistor means, wherein a control terminal of said third transistor means is coupled to said third node.

7. Circuit according to claim 1, further comprising a sixth current path including a sixth current source and a seventh current source coupled at a fifth node, said sixth current source is configured to be controlled by a signal of said second node and said seventh current source is configured to be controlled by a signal of said third node, wherein said second current source is configured to be controlled by a signal from said fifth node.

8. Circuit according to claim 1, wherein said respective current sources are implemented by respective transistor means.

9. Circuit according to claim 8, wherein said transistor means of said circuit either are all npn-transistors or are all pnp transistors.

10. A radio frequency power amplifier, a circuit in radio frequency tag, or a circuit in a satellite microwave front-end comprising a current sourcing circuit for generating a current proportional to absolute temperature comprising a circuit according to claim 1.