Design of a CMOS Adaptive Charge Pump with Dynamic Current Matching

A novel structure for a charge pump circuit is proposed, in which the charge-pump （CP） current can adaptively regulated according to phase-locked loops （PLL） frequency synthesis demand. The current follow technology is used to make perfect current matching characteristics, and the two differential inverters are implanted to increase the speed of charge pump and decrease output spur due to theory of low voltage difference signal. Simulation results, with 1st silicon 0. 25μm 2. 5 V complementary metal-oxide-semiconductor （CMOS） mixed-signal process, show the good current matching characteristics regardless of the charge pump output voltages.

A New 1-V Second-Order Temperature-Compensated Current Reference

A new bipolar temperature-compensated current reference is proposed. The first-order temperature compensation is achieved by the idea of self temperature-compensation configuration exploiting the temperature coefficient of a combined resistor. The second-order compensation employs a VBE-tracking thermal-startup technique to obtain improved temperature performance. The proposed circuit can operate down to a 1-V supply. A temperature coefficient of 46.6×10?6/℃ [0, 100℃] at a 1-V supply and a supply regulation of 0.036%/V at 25℃ are achieved. Compared with present works, the proposed circuit shows better results of the temperature coefficient and supply regulation. The current matching issue frequently encountered in current references is also discussed in detail.

Designing of 1 eV GaNAs/GaInAs superlattice subcell in current-matched four-junction solar cell

A reasonably-thick GaNAs/GalnAs superlattice could be an option as a roughly 1 eV subcell to achieve high-effiCiency multi-junction solar cells on a lattice-matched Ge substrate. A detailed consideration of a high- efficiency design for a GaInP/GaAs/1 eV/Ge device is presented. Calculations have been done for this structure to obtain the confined energies of the electrons and holes by utilizing the Kronig-Penney model, as well as the absorption coefficient and thereby the external quantum efficiency. The effect of well layers, GaNAs or GaInAs, on the absorption and photocurrent density under the AM 1.5 condition is discussed in order to realize a requirement of current matching in the four-junction solar cells. The management of these considerations implies the feasibility of the GaNAs/GaInAs superlattice subcell design to improve the overall conversion efficiency of lattice matched GaInP/GaAs/1 eV/Ge cells.

Numerical simulation of the performance of the a-Si:H/a-SiGe:H/a-SiGe:H tandem solar cell

The computer program AMPS-1D（analysis of microelectronic and photonic structures） has been employed to simulate the performance of the a-Si：H/a-SiGe：H/a-SiGe：H triple-junction solar cell at the radiation of AM1.5G（100 mW/cm2/ and room temperature. Firstly, three sub-cells with band gaps of 1.8, 1.6 and 1.4 eV are simulated, respectively. The simulation results indicate that the density of defect states is an important factor, which affects the open circuit voltage and the filling factor of the solar cell. The two-step current matching method and the control variate method are employed in the simulation. The results show that the best solar cell performance would be achieved when the intrinsic layer thickness from top to bottom is set to be 70, 180 and 220 nm, respectively. We also optimize the tunnel-junction structure of the solar cell reasonably, the simulation results show that the open circuit voltage, filling factor and conversion efficiency are all improved and the S-shape current density–voltage curve disappears during optimizing the tunnel-junction structure. Besides, the diagram of the energy band and the carrier recombination rate are also analyzed. Finally, our simulation data are compared to the experimental data published in other literature. It is demonstrated that the numerical results agree with the experimental ones very well.

AlGaAs/GaAs tunnel junctions in a 4-J tandem solar cell

The Ⅲ-Ⅴ compound tandem solar cell is a third-generation new style solar cell with ultra-high efficiency. The energy band gaps of the sub-cells in a GaInP/GaAs/InGaAs/Ge 4-J tandem solar cell are 1.8, 1.4, 1.0 and 0.7 eV, respectively. In order to match the currents between sub-cells, tunnel junctions are used to connect the sub-cells. The characteristics of the tunnel junction, the material used in the tunnel junction, the compensation of the tunnel junction to the overall cell＇s characteristics, the tunnel junction＇s influence on the current density of sub-cells and the efficiency increase are discussed in the paper. An A1GaAs/GaAs tunnel junction is selected to simulate the cell＇s overall characteristics by PC 1 D, current densities of 16.02, 17.12, 17.75 and 17.45 mA/cm^2 are observed, with a Voc of 3.246 V, the energy conversion efficiency under AM0 is 33.9%.