Programmable Floating Gates Filters Matt Kucic and Paul

Programmable Floating Gates Filters Matt Kucic and Paul Hasler Integrated Computational Electronics (ICE) Laboratory Georgia Institute of Technology

Overview of Floating-Gate Devices Information Storage Floating-Gate Transistor Modifying Floating-Gate Charge • UV photo-injection • Electron tunneling • Hot-electron injection

Programming a FG Multiply by weight V tun X D/A Vin + V in + D/A I Computing in Memory! Provide a bias current

Analog Computing Arrays

Electron Transport in a Hot. Electron Injecting n. FET

p. FET Hot-Electron Injection The injected electrons are generated by hole impact ionizations. **Injection current is proportional to source current, and is an exponential function of Fdc. Vinj = 430 m. V

Programming a FG V Injection • Gate voltage required to create a channel for current to flow tun + V in + • Large Source to drain voltage required for high field to make electron hot I 2 conditions must be meet for injection

Basic Programming Structure Injection • Requires Voltage across the Source-Drain • Requires Voltage on the Gate Tunnelling • Requires a voltage across the tunneling cap.

Basic Programming Structure Injection Ø Both: Gate: Columnisolation Device isolation Ø Source-Drain: Row isolation

Electron Tunneling (oxide voltage)-1 Increasing the applied voltage decreases the effective barrier width The range of tunneling currents span many orders of magnitude.

Programming a FG V + V in tun Tunneling • Voltage across the tunneling capacitor determines if tunneling occurs. • Voltage on gate will change this voltage.

HV Decoding Basic Programming Structure Tunneling Ø Device Columnisolated Require HV switches More area required

Basic Programming Structure

Programming a FG V Bring chip up to program voltage Bring drain up to match Vds(run) Set Gate volt to read current Read Current through device Calculate next pulse on drain Pulse Drain voltage Rinse and repeat tun + V in A + - Offchip

Basic Programming Structure

Floating Vin Bandpass Filters 1 2 3 4 5 Time-Frequency Decomposition Filter Spacing • Exponential • Linear • General (Floating-gate storage) n

Fourier-Based Programmable Filters Vin Bandpass Filters, Bandpass Exp Spaced Filters (Hard in DSP) W 11 W 12 W 13 W 14 W 15 W 1 n Iout 1 W 22 W 23 W 24 W 25 W 2 n Iout 2 Programmable Analog Filter Analogous to FFT / IFFT DSP based filters

Fourier-Based Programmable Filters Vin W 11 W 12 W 13 W 14 W 15 W 1 n Iout 1 W 22 W 23 W 24 W 25 W 2 n Iout 2

Capacitively Coupled Current Conveyers AFGA C 4 Tunneling Circuit Injection Circuit Hasler, Kucic, and Minch, Midwest 99

Differential C 4 - Bandpass • Reduces 2 nd harmonic from C 4 • Allows for multiplier band weighting • Each side biased same

Different Frequency Responses Bandpass varying tl and th Bandpass with tl near th 1 v 10 v 37. 5. 2 Vt p= 70 9 v 28 v Gain Vt p= . 3 Vt p= v 74 . 2 1 v. 50 tp = 2 . 2. 3 tp = 2 V V v . 37 105 4 v 89 Gain . 5 60 Frequency(Hz) 104 n= Vt 4 v . 54 103 . 45 9 v 1 =0 Vt 102 = tn . 58 0. 2 10 n= Vt =0 Vt 1 V 0 v . 53 . 61 7 v V =0 Vt tp = 2. 5 6 10 10 -1 10 -2 10 102 103 Frequency(Hz) 104 105

Bank of tunable bandpass filters

Fourier-Based Programmable Filters Vin W 11 W 12 W 13 W 14 W 15 W 1 n Iout 1 W 22 W 23 W 24 W 25 W 2 n Iout 2

Floating-Gate Multiplication Vdd 23 Vtun Vdibl + Vin + Iout Output Current (n. A) 22 21 20 W=0 19 W = 0. 35 18 17 W=0 W = -0. 35 W = -0. 70 W = 1. 40 W = -1. 40 -0. 5 -0. 4 -0. 3 -0. 2 -0. 1 0. 2 Differential input (V) 0. 3 0. 4 0. 5

Programmable Analog DFT 10 10 1 10 0 0 Individual Bandpass Filter Output 10 -1 -1 10 -2 Fourier Filter Output 10 10 -2 -3 10 0 10 -3 10 1 10 2 10 3 Frequency (Hz) 10 4 10 -4 10 5 Output Amplitude of Bandpass Filter (V-rms) Output Amplitude of Fourier Filter (m. A-rms) 10

Programmed Filter 10 -3 10 -4 10 -5 10 -6 50 Hz 100 k. Hz

Conclusions • Elegant and robust programmable filter. • Scalable – Easy to place additional taps/summing lines • Devices retains programming when no power applied. • Fabricated in standard processes • Programming scheme can be used on other FG circuits • Floating Gates CAN be used in circuits where more than 2 -3 Floating Gate transistors are needed.