Stacked double-flux-quantum output amplifier

Abstract

A suitable data link from RSFQ to semiconductor electronics remains challenging. We report an output amplifier that uses a new pulse multiplier circuit. The pulse multiplier consists of several stages arranged in series; a double-flux-quantum gate at each stage promotes the SFQ pulse to the next stage. Characteristics of the circuit design are: 1) DC power. As with the DFQ gate, every unshunted Josephson junction in the amplifier is loaded by critically-damped junctions that prevent voltage-state modes. 2) Equal rise and fall times that scale with output amplitude. In our case, 50 ps rise and fall time and 1-2 mV output amplitude can be realized, which is ideal for a data rate of 10 Gb/s. 3) Quantum accurate voltage multiplication independent of bias current. 4) Non-return-to-zero (NRZ) operation. The circuit was designed and successfully tested in our 8 kA cm 2 foundry process. A 60 GHz pulse train, generated on-chip, was gated with RSFQ logic to produce a data pattern that was then fed into a pulse multiplier of either ten or twenty stages. Voltage multiplication was observed with operating margins of 21% on bias current. Fast rise time was directly observed; unfortunately, fall time was spoiled by ringing on a 1 ns time scale. It is plausible that small changes to the physical layout of the circuit would produce desired operation.Index Terms-Author, please supply your own keywords or send a blank e-mail to keywords@ieee.org to receive a list of suggested keywords.

9 bit superconductive single‐flux‐quantum digital‐to‐analogue converter

“…2b. It comprises 99 double-flux-quantum amplifier (a 99-stage DFQA) [13,14]. Besides critically damped JJs with shunting resistors, underdamped JJs without shunting resistors are employed to multiply the number of SFQ pulses.…”

Modified Double-Flux-Quantum Amplifier for Bipolar Voltage Multiplication

“…The DFQA was proposed for a voltage driver [9]. We have verified the characteristics of a 1000-fold DFQA [10], [11].…”

“…In this paper, we present a bipolar voltage amplifier (BVA) based on a double flux quantum amplifier (DFQA) [9]− [11] to generate intrinsic bipolar voltage in an SFQ-DAC. We have designed a 19-fold BVA and verified its characteristics.…”

Measurement of Superconductive Voltage Drivers up to 25 Gb/s/ch

“…This paper reports on an SVD that generates non-return-to-zero (NRZ) outputs, in contrast to our previous SVDs that generated return-to-zero (RZ) outputs [5], [7]. A few NRZ SVDs were already reported [3], [13]. Since the fundamental frequency of an NRZ signal is half that of an RZ signal (the duty ratio is assumed to be 50%), the digital throughput can be doubled by changing the signal format from RZ to NRZ with the same I/O cables and packaging.…”