Low noise-high linearity HEMT-HBT composite

Abstract: 4-terminal HEMT-HBT composite devices, based upon monolithically integrated HEMT-HBT technology and configured in various topologies, are useful in a wide range of applications which currently utilize discrete MMICs. In particular, the 4-terminal topologies are easily configured as 3-terminal composite devices useful in various 2-port and 3-port MMIC circuit applications, such as low noise-high linearity amplifiers as well as mixers, which provide the benefits of a reduction in size, as well as corresponding cost while providing better performance than utilizing either HEMT or HBT devices individually.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to monolithic microwave integrated circuits (MMICs) and more particularly to low noise-high linearity MMICs formed from monolithically integrated high-electron mobility transistor (HEMT) and heterojunction bipolar transistor (HBT) devices, useful in a wide range of applications, which reduce the size, cost, as well as power consumption of such applications while providing relatively better overall performance capability than utilizing either HEMT or HBT devices individually. 2. Description of the Prior Art Various applications are known in which low noise and high linearity performance is required. Examples of such applications include low noise amplifiers (LNAs), variable gain amplifiers (VGAs), transmit/receive (T/R) modules, power amplifiers, transimpedance amplifiers and optical receivers used in various products including wireless products, cellular telephony, fiber optic data links, portable electronics and the like. In many of such applications, it is known to utilize a high-electron mobility transistor (HEMT) for its low-noise figure performance and a heterojunction bipolar transistor (HBT) for its high-linearity performance. Because of the limited topologies availabe in known monolithic microwave integrated circuits (MMICs) oftentimes, separate MMICs are used. In certain applications, for example, in applications where there are space constraints, the use of multiple MMICs is undesirable. In addition, the use of multiple MMICs increases the cost as well as the complexity and power consumption of the system in which such devices are used. MMICs have been developed in which HEMT and HBT technologies have been monolithically integrated in a single MMIC, for example, as disclosed in copending EP Patent Application No. EP-A-710984, published on May 8, 1996 and having a priority of November 2, 1994. However, the topologies of such integrated HEMT-HBT MMICs are limited. While such MMICs are useful in certain applications, many applications as discussed above require different circuit configurations and thus in such applications, separate HEMT and HBT MMICs are used. As discussed above, the use of multiple MMICs increases the cost, as well as the complexity of the circuitry and is relatively limited in applications having size constraints. From Kobayashi et al., "A Monolithic HEMT-HBT Direct-Coupled Amplifier with Active Input Matching" IEEE Microwave and Guided Wafe Letters, Vol. 6, number 1, pages 55-57 and from Kobaysahi et al. "A Novel Monolithic LNA Integrating a Common-Source HEMT with an HBT Darlington Amplifier", IEEE Microwave and Guided Wave Letters, Vol. 6, No. 12, pages 442-444 it is known to monolithically integrate a HEMT with a HBT to realize an amplifier having an input port and an ouput port. The gate terminal of the HBT is connected with either the source or the drain terminal of the HEMT. From US 5 068 282 a high frequency amplifying device is known comprising monolithically integrated HEMTs and HBTs. The gate terminal of the HBT is electrically connected to the source terminal of the HEMT. Furthermore, a microwave amplifier comprising a cascode connection of a bipolar transistor with a field effect transistor is known e.g. from US-A-4 688 267. SUMMARY OF THE INVENTION It is an object of the present invention to solve various problems in the prior art. It is yet another object of the present invention to provide microwave monolithic integrated circuits (MMICs) with integrated HEMT-HBT devices configured in various topologies that are useful in a wide range of applications. Briefly, the present invention relates to a 4-terminal MMIC as defined in claim 1 formed from monolithically integrated HEMT-HBT technology in various topologies useful in a wide range of applications which currently utilize multiple discrete MMICs. BRIEF DESCRIPTION OF THE DRAWING These and other advantages of the present invention will become apparent with reference to the following specification and attached drawing, wherein: FIG. 1 is schematic representation of a HEMT-HBT 4-terminal composite device illustrating a topology in accordance with the present invention; FIG. 2 is a schematic diagram of a low noise-high linearity HEMT common-source HBT common-base 3-terminal composite device in accordance with the present invention; and FIG. 3 is a schematic diagram of a low noise-high linearity HEMT common-source HBT 3-terminal mixer device in accordance with the present invention. DETAILED DESCRIPTION OF THE INVENTION As mentioned above, low noise and high linearity performance is required in a relatively wide range of applications. In order to achieve such performance objectives, high-electron mobility transistors (HEMTs) and heterojunction bipolar transistor (HBT) devices are known to be used for such applications. Other than a relatively few topologies formed as monolithic microwave integrated circuits (MMIC) in which the HEMT and HBT technologies are integrated, many known low noise and high linearity performance applications are known to use separate HEMT and HBT MMICs. The present invention provides HEMT-HBT composite device topologies that combine key performance and device properties in order to provide advantages in size, performance and circuit functionality. The performance capabilities of the HEMT device technology, HBT device technology and composite HEMT-HBT devices in accordance with the present invention is illustrated in Table 1. Device & Technology Gm Noise Figure IP3 (Linearity) Power Efficiency Frequency Capability HBT High Medium High High dc->20 GHz HEMT High Low Medium Medium dc->100 GHz HEMT-HBT Topology (FIG. 2) CS-CB High ≈ Gm hemt Low High High dc->20 GHz As illustrated in Table 1, the overall capability of the HEMT-HBT composite devices in accordance with the present invention provide a combination of low noise and high linearity characteristics, which cannot be obtained from either the HEMT or .HBT devices alone. In addition, the HEMT-HBT monolithic composite devices can provide better performance than obtainable from an equivalent discrete hybrid (MIC) implementation of the same composite device topologies. The topologies for the composite HEMT-HBT devices in accordance with the present invention are illustrated in FIG. 1. As shown, the topology is configured as a 4-terminal device and includes a low noise HEMT device that is directly coupled to a high linearity HBT device. Each of the terminals are defined by an open circle. By directly coupling the HEMT and HBT, the composite devices will maintain low noise figure characteristics of the HEMT and the high linearity characteristics of the HBT. In order to provide a relatively wide range of applications, each of the topologies are configured with four terminals to enable the topologies to apply in a relatively wide range of circuit applications, including various amplifiers and mixers as discussed below. The 4-terminal topology is shown with electrical coupling to terminals for connection to external circuits. These terminals are defined by an open circle. As discussed below, one of the terminals can be grounded and eliminated to form 3-terminal devices and 2-port and 3-port circuit networks as discussed below. A second 4-terminal topology of a composite HEMT-HBT device is illustrated in FIG. 1 and generally identified with the reference numeral 48. The composite device 48 includes a HEMT 50 and an HBT 52. In this topology, the drain electrode of the HEMT 50 is directly connected to the emitter electrode of the HBT 52. The gate and source electrodes of the HEMT 50 are connected to external terminals 54 and 56, respectively, while the base and collector electrodes of the HBT 52 are connected to external terminals 58 and 60, respectively, to form the 4-terminal HEMT-HBT composite device 48. As shown in FIGS. 2-3, the 4-terminal topologies, illustrated in FIGS. la and 1b, can be configured as 3-terminal devices which can be used as a basis for various useful 2- and 3-port circuit configurations. In these applications like reference numerals are used to identify like components and open circles are used to define the composite device terminals. The 4-terminal HEMT-HBT topology 48, illustrated in FIG. 1b, can also be configured into 3-terminal composite devices, which can be used for 2-port low noise-high linearity amplifiers or 3-port mixer applications as illustrated in FIGS. 2 and 3, respectively. Using like reference numerals for components with similar function, the HEMT-HBT composite device, illustrated in FIG. 2, generally identified with the reference numeral 90, is configured as a common-source HEMT 50 with a common-base HBT 52. In particular, the source electrode of the HEMT 50 is coupled to ground, as is the base electrode of the HBT 52, thus eliminating the external terminals 56 and 58, illustrated in FIG. 1b. An external load resistor R L 92 may be connected between ground and external terminal 94 to define an output load impedance at the output of the resulting 2-port HEMT common-source HBT common-base amplifier 90, as illustrated in FIG. 2. The composite device 90, illustrated in FIG. 2, combines a common-source HEMT with a common-base HBT to form a hybrid cascode. An important aspect of this configuration is that the device can provide high input and high output impedances simultaneously. The common-source configured HEMT 50 provides optimally low noise figure performance, while the common-base configured HBT 52 provides wideband high linearity. A common advantage of any cascode configuration is that the Miller capacitance multiplication of the input device is reduced. In addition, the low loss HEMT input and HBT output characteristics of the HEMT-HBT cascode illustrated in FIG. 2 allows for the construction of low loss matching networks to tune the input HEMT 50 for noise and the output HBT 52 for linearity and power. The high input and output impedance provide optimal use of parallel feedback from the collector output of the HBT 52 to the gate input of the HEMT 50. By implementing the HBT 52 in a common-base configuration, the composite device 90 will have relatively low noise-high linearity and high frequency capability, attractive for various known high voltage gain applications. The effective transconductance of the composite device 90 is provided by equation (1), while the input and output impedances are provided in equations (2) and (3). (1) Gm eff ≈ { Gm HEMT 1 + Gm HEMT * r s } * α 0 (2) Z in (s) ≈ r g + r s + r i + 1 s * C gs (3) Z out ( s ) ≈ (β( s ) + 1) * r 0 where β( s ) ≈ β 0 1 + s/ω T An alternate configuration of the topology illustrated in FIG. lb is shown in FIG. 3 and identified with the reference numeral 96. In this configuration the HEMT 50 is configured as a common source, thus eliminating the external terminal 56. By utilizing the base input of the HBT 52 as a third port, a HEMT-HBT 3-port composite device 96, configured as an active mixer cell, is provided; analogous to a dual-gate FET active mixer. The low noise HEMT gate input 54 is used for the receiver RF port, while the HBT base input may be used as an LO (local oscillator) input port. The HBT collector terminal 60 may be used, for example, to extract out the IF frequency. The devices disclosed herein can be fabricated by known methods as disclosed in "Monolithic HEMT-HBT Integration by Selective MBE," by D.C. Streit, D.K. Umemoto, K.W. Kobayashi and A.K. Oki, IEEE Transactions on Electron Devices, Vol. 42, No. 4, April 1995, pp. 618-623; "A Monolithic HBT-Regulated HEMT LNA by Selective MBE.," by D.C. Streit, K.W. Kobayashi, A.K. Oki and D.K. Umemoto, Microwave and Guided Wave Letts., Vol. 5, No. 4, April 1995, pp. 124-126; EP Patent Application EP-A-710984, published on May 8, 1996 and having a priority of November 2, 1994. In addition to the HEMT-HBTs, the devices, as shown in the schematic drawings, include thin-film resistors (TFR) and metal-insulator-metal (MIM) capacitors, also known in the art.

Claims: A 4-terminal monolithic microwave integrated hybrid cascode circuit providing high input and high output impedances simultaneously, comprising: a high electron mobility transistor (50) having gate, drain and source terminals and providing low noise figure performance; and a heterojunction bipolar transistor (52) having base collector and emitter terminals and providing wideband high linearity, said emitter terminal of said heterojunction bipolar transistor (52) being directly electrically connected to said drain terminal of said high electron mobility transistor (50). The 4-terminal monolithic microwave integrated hybrid cascode circuit of claim 1, wherein one of said terminals is connected to ground in order to obtain a 3 terminal device. The monolithic microwave integrated cascode circuit as recited in claims 1 or 2, wherein said source terminal of said high electron mobility transistor (50) is electrically coupled to ground, said base terminal of said heterojunction bipolar transistor (52) is electrically coupled to ground, and wherein said gate terminal of said high electron mobility transistor (50) and said collector terminal of said heterojunction bipolar transistor (52) are each electrically coupled to a terminal (54, 60) for connection to an external electrical circuit. The monolithic microwave integrated cascode circuit as recited in claims 1 or 2, wherein said source terminal of said high electron mobility transistor (50)is electrically coupled to ground and said gate terminal of said high electron mobility transistor (50) and said base and collector terminals of said heterojunction bipolar transistor (52) are each electrically coupled to a terminal (54, 58, 60) for connection to an external electrical circuit.

Inventors: KOBAYASHI KEVIN WESLEY, OKI AARON KENJI, STREIT DWIGHT CHRISTOPHER, UMEMOTO DONALD KATSU, KOBAYASHI, KEVIN WESLEY, OKI, AARON KENJI, STREIT, DWIGHT CHRISTOPHER, UMEMOTO, DONALD KATSU
Applicants: TRW INC, TRW INC.
Application year: 1997
Main classification: H03F3
IPC codes: H01L27, H03D7, H03F3, H01L21, H03F1