||This thesis is composed of a biomedical sensing system design and a novel circuit|
design of 5T SRAM (static random access memory, SRAM). The first topic is a CEA (carcinoembryonic
antigen, CEA) readout system development, while a static random access
memory with leakage sensor and read delay compensation is the second.
The first topic investigates a CEA measurement readout system. The core of this
system is the readout circuit. By taking advantage of the characteristics that the resonant
frequencies of the loaded FPW (flexural plate-wave, FPW) biosensor will shift, we can
detect the maximum voltage of the various sine wave signals fed into the biosensors when
the sine wave signal frequency meets the resonant frequency. The difference of the frequency
change, which also indicates the concentration of the biosensor, can be estimated
by a look-up table. The frequency shift of the biosensors can be readout in 10 minutes
by physical measurement to attain the linearity R2 of 0.9772, and the maximum error of
In the second topic, a 4+1 kb SRAM with leakage sensor and read delay compensation
is demonstrated using 40 nm CMOS process, where single-ended 5T loadless SRAM cells are used. The energy per access is found to be 0.9411 pJ and the read delay is reduced 35.58% at the expense of 3.64% area overhead. The leakage sensor and compensation circuits are carried out by dummy SRAM cells to mimic the leakage currents therein. A warning signal will be sent and activates the compensation circuit to speed up the read access and lower the power consumption when the dummy SRAM cells are threatened by leakage currents.