Yoshiko Ikeda

A novel resonant-type GaAs SPDT switch IC with low distortion characteristics for 1.9 GHz personal handy-phone system

A GaAs SPDT switch IC operating at a low power supply voltage of 2.7 V has been developed for use in Personal Handy-Phone System in the 1.9 GHz band. In combination with MESFETs with low on-resistance and high breakdown voltage, the resonant-type switch IC utilizes stacked FETs and an additional shunt capacitor at the receiver side in order to realize low insertion loss, high isolation and low distortion characteristics. An insertion loss of 0.55 dB and an isolation of 35.8 dB were obtained at 1.9 GHz. The IC also achieved a second order distortion of -54.3 dBc and an adjacent channel leakage power of -66 dBc at 600 kHz apart from 1.9 GHz at 19 dBm output power.

Non-destructive current measurement for surface mounted power MOSFET on VRM board using magnetic field probing technique

This paper proposes nondestructive current measurement for surface mounted power MOSFET on VRM board using the micro-magnetic probing technique to facilitation discussion of the self-turn-on phenomenon. A notable feature of the proposed technique is that the sensor part is much smaller than that of conventional methods because this method measures the intensity of a partial magnetic field caused by wire bonding inductance, whereas the conventional method employs a loop coil structure around the current flow. The small sense part enables measurement of the VRM board itself just by setting the magnetic probe on the MOSFET package. A calibration technique is introduced to reproduce current waveform and we confirm that the obtained current waveform agrees with that obtained by the conventional Current Transformer. Using the proposed technique, we successfully detect shoot through current waveform for high-side power MOSFET during self-turn-on phenomenon in VRM board. We also sense non-uniform current flow among 3 parallel low-side power MOSFETs caused by board layout location. This study demonstrates the capability of sensing VRM board transient current and indicates the importance of board GND layout distribution behavior in determining highly accurate trade-off between switching loss and self-turn-on loss.

A 20 GHz 8 bit multiplexer IC implemented with 0.5 /spl mu/m WN/sub x//W-gate GaAs MESFET's

An ultrahigh-speed 8 bit multiplexer (MUX) has been developed for future-generation optical-fiber communication systems having a data rate of 20 Gb/s. This IC was fabricated using a 0.5 /spl mu/m WN/sub x//W-gate GaAs MESFET process based on optical lithography, ion implantation, and furnace annealing for good reproducibility and high throughput. The WN/sub x//W bilayer gate has a low sheet resistance, improving the circuit high frequency performance. To attain 20 GHz operation, advanced circuit techniques for the source-coupled FET logic (SCFL) were introduced. A cross coupled source-follower (CCSF) was developed mainly for the highest speed buffers to enhance the bandwidth. The first-stage T-type flip-flop was designed with optimization techniques and operated up to 21.1 GHz. >

A symmetric GaAs MESFET structure with a lightly doped deep drain for linear amplifiers operating with a single low-voltage supply

An improved symmetric GaAs MESFET structure with a lightly doped deep source/drain is proposed for application to power amplifiers in mobile communication terminals. With lightly doped deep drain, the impact ionization falls as the electron current expands and the current density decreases. Thus, the breakdown voltage rises, while a high transconductance and low parasitic resistance are maintained. Furthermore, the symmetric structure suits for mass production because of its fabrication process without mask alignment precision. This structure was fabricated using the WNx/W self-aligned gate process, and DC and RF characteristics were evaluated. The power-added efficiency was 37% at an adjacent channel leakage power of -55 dBc for 37%-shift QPSK modulated input signals at 1.9 GHz with a single positive supply voltage of 3 V. The efficiency was also high at a lower supply voltage: 34% at 1.2 V.

10A 12V 1 chip digitally-controlled DC/DC converter IC with high resolution and high frequency DPWM

This paper introduces a 10 A 12 V single chip digitally-controlled DC/DC converter IC based on the low cost 0.6 um BiCD process. This IC includes the digital pulse width modulator (DPWM) module with the dead-time programmability. The average time resolution is 1.22 ns at the clock frequency 25 MHz on 0.6 um process. This resolution is as same as that for the counter-based DPWM with the clock frequency 817 MHz. The chip adopted low impedance metal bump technology for reducing a parasitic interconnection resistance in the power stage. The fabricated chip achieves a low on resistance 9.7 mOmega in the 20 V output LDMOS (@drain current=5 A, gate voltage=5 V). The maximum efficiency is 86.4% at output current 5 A when the input voltage, the output voltage and switching frequency and the dead-time are 12 V, 1.3 V, 780 KHz and 15 ns, respectively. The maximum voltage deviation and transient response time are 42 mV and 8 us, respectively in step-load (5 A to 10 A) transient response.

Advanced cathode and anode injection control concept for 1200V SC(Schottky controlled injection)-diode

At ISPSD2013, we presented an SC-diode that realizes low forward voltage drop (VF), low reverse recovery loss and low leakage current at high temperature of over 175 °C, with a combination of very low injection efficiency and high carrier lifetime. This paper proposes an advanced low injection cathode concept with N Schottky region enabling the SC-diode to obtain excellent fast recovery characteristics, realizing a range of 10 kH switching frequency. We discuss a balance of injection efficiency between two sides (anode and cathode), which is very important for reducing voltage ringing during reverse recovery under low current turn-on condition of IGBTs. Furthermore, we have obtained high reverse recovery ruggedness by controlling impact ionization position where is only bottom of deep P anode layer.

20 GHz 8b multiplexer implemented with 0.5 /spl mu/m WNx/W-gate GaAs MESFETs

High-speed multiplexers (MUXs) are key components in optical-fiber communication systems. MUXs with a higher operating frequency are desirable to realize increases in data transmission capacity. Furthermore, MUXs with a higher number of bits are also desirable to reduce the number of high-speed system components. This 20 GHz 8b MUX is based on source-coupled FET logic (SCFL) and fabricated using a 0.5 /spl mu/m GaAs MESFET process based on conventional optical lithography and ion implantation. This is the fastest reported 8b MUX.<<ETX>>