Table 2.

Optimized p-type epitaxial piezoresistive cantilevers for several choices of instrumentation amplifier. Optimization was performed for operation from 1 Hz to 50 kHz with a minimum thickness of 1 μmW, and maximum bias voltage of 10 V. Three amplifiers were considered: TI INA103, AD622, and AD623. The amplifiers were chosen to represent several price points and noise levels. Although the integrated noise of the AD622 and AD623 are 3 times and 17 times greater than that of the INA103, the minimum detectable force only increases by 10% and 70%, respectively. As the instrumentation amplifier noise increases, the piezoresistor is made shorter and thinner, which increases the sensitivity, while the increased 1∕f noise due to the reduction in N negligibly affects the overall noise while it is less than the amplifier noise.

Cantilever	1	2	3
Amplifier	INA103	AD622	AD623
fmin (Hz)	1	1	1
fmax (kHz)	50	50	50
l (μm)	74	74	74
w (μm)	2	2	2
t (μm)	1	1	1
lpr∕l	0.33	0.31	0.21
tpr∕t	0.25	0.23	0.16
n (cm−3)	4.4×1019	4.4×1019	4.4×1019
Fmin (pN)	134	147	230
SF (V∕N)	3.2×104	3.3×104	3.8×104
β*	0.38	0.39	0.43
$\overline{V_{\text{noise}}}$ (V)	4.3×10−6	4.9×10−6	8.8×10−6
$\overline{V_J}$	2.9×10−6	2.9×10−6	2.9×10−6
$\overline{V_H}$	3.1×10−6	3.4×10−6	4.9×10−6
$\overline{V_A}$	4.0×10−7	2.0×10−6	6.7×10−6
fcorner (kHz)	5.5	6.5	13.5
N	5.5×108	4.7×108	2.2×108