Browsing by Author "Bosch, Roland"

Now showing 1 - 6 of 6

Open Access
14 GHz bandwidth MSM photodiode AlGaAs/GaAs HEMT monolithic integrated optoelectronic receiver
(1993) Hurm, Volker; Ludwig, Manfred; Rosenzweig, Josef; Benz, Willi; Berroth, Manfred; Bosch, Roland; Bronner, Wolfgang; Hülsmann, Axel; Köhler, Klaus; Raynor, Brian; Schneider, Joachim
A monolithic optoelectronic receiver consisting of an MSM photodiode and a two-stage amplifer has been fabricated using an enhancement/depletion 0.3 μm recessed-gate AlGaAs/GaAs HEMT process. The band-width of 14.3 GHz implies suitability for transmission rates of up 20 Gbit/s. The transimpendance is 670 Ω (into 50 Ω) and the projected sensitivity is 16.4 dBm (BER = 10 -9).
Open Access
An 18-34-GHz dynamic frequency divider based on 0.2-μm AlGaAs/GaAs/AlGaAs quantum-well transistors
(1993) Thiede, Andreas; Berroth, Manfred; Nowotny, Ulrich; Seibel, Jörg; Bosch, Roland; Köhler, Klaus; Raynor, Brian; Schneider, Joachim
The design and performance of a dynamic frequency divider was presented. This digital IC demonstrates the ability of the authors' AlGaAs/GaAs/AlGaAs quantum-well FETs with gate lengths of 0.2 μm. Stable operation was achieved in the frequency range from 18 GHz up to 34 GHz with a power consumption of 250 mW. To the authors' knowledge, this is the best result ever reported for HEMT circuits, and is similar to the frequency limit achieved by use of AlGaAs/GaAs HBTs.
Open Access
Broad-band determination of the FET small-signal equivalent circuit
(1990) Berroth, Manfred; Bosch, Roland
A method to determine the broadband small-signal equivalent circuit of field-effect transistors (FETs) is proposed. This method is based on an analytic solution of the equations for the Y parameters of the intrinsic device and allows direct determination of the circuit elements at any specific frequency or averaged over a frequency range. The validity of the equivalent circuit can be verified by showing the frequency independence of each element. The method can be used for the whole range of measurement frequencies and can be applied to devices exhibiting severe low-frequency effects.
Open Access
Frequency dependent CV measurements of GaAs/AlGaAs heterostructures
(1989) Berroth, Manfred; Bosch, Roland; Hurm, Volker
A procedure is described to determine the carrier density profile in the channel of a FET by evaluating S-parameters measured over a broad frequency range. Applying this method to GaAs/AlGaAs heterostructures, a frequency dispersion of the gate capacitance has been found, which is attributed to a parasitic conducting channel.
Open Access
High frequency equivalent circuit of GaAs depletion and enhancement FETs for large signal modelling
(1990) Berroth, Manfred; Bosch, Roland
For the design of digital circuits as well as for power amplifiers, the nonlinear modelling of GaAs FETs is a necessity. We use an extended equivalent circuit, which takes into account the gate current of positive biased transistors as well as the symmetrical nature of the devices at low drain voltages. A fast method to determine the elements of the equivalent circuit from measured S-parameters is presented which delivers for the first time good agreement for all operating points. A valid large signal description of the device can be obtained by implementing the bias dependences of the intrinsic elements into a circuit simulator like SPICE.
Open Access
High-frequency equivalent circuit of GaAs FET's for large-signal applications
(1991) Berroth, Manfred; Bosch, Roland
The application of GaAs field effect transistors in digital circuits requires a valid description by an equivalent circuit at all possible gate and drain bias voltages for all frequencies from DC up to the gigahertz range. An equivalent circuit is presented which takes into account the gate current of positively biased transistors as well as the symmetrical nature of the devices at low drain voltages. A fast method of determining the elements of the equivalent circuit at all bias points without frequency limitations is presented. Direct computation from analytical expressions, without iteration, allows this parameter extraction procedure to be used for real-time on-wafer parameter extraction. Large-signal calculations are possible by inserting the voltage dependences evaluation for the elements into suitable simulation programs, such as SPICE.