AD620 Instrumentation Amplifier Module

The AD620 instru­men­ta­tion ampli­fi­er mod­ule pro­vides a plat­form for ampli­fi­ca­tion of small AC or DC sig­nals from ana­log sen­sors, strain gauges, trans­duc­ers and sim­i­lar devices.PACKAGE INCLUDES:AD620 Instru­men­ta­tion Ampli­fi­er Mod­ule1×4 male head­er strips (x2)KEY FEATURES OF AD620 INSTRUMENTATION AMPLIFIER MODULE:Adjustable gain of 1.5 to 1000xAdjustable off­set120kHz band­width (gain = 100x)Input sig­nal range of 100uV – 300mVMax­i­mum out­put range of Vin – 2V3.5–10V oper­a­tion (Vin)The AD620 instru­men­ta­tion ampli­fi­er mod­ule is handy for ampli­fy­ing small AC or DC sig­nals.Module PowerAD620 Instru­men­ta­tion Ampli­fi­er Mod­ule Reverse Engi­neered Schemat­icThe mod­ule can be pow­ered from 3.5 to 10V on the VIN pin and adja­cent GND pin.The VIN volt­age pass­es through a 10 ohm resis­tor and con­nects to the Vs pin on the AD620.  We denote this as V on our reverse engi­neered schemat­ic.The 7660 volt­age con­vert­er (charge pump) IC also takes in the V volt­age and gen­er­ates a neg­a­tive volt­age for the ‑Vs pin on the AD620 which we labeled as V-.  This gives the AD620 both pos­i­tive and neg­a­tive pow­er rails.   V and V- also pow­er the LM358 Op AmpThe neg­a­tive volt­age is also brought out to the pin labeled V- on the out­put side of the board in case you want to tap into it.  Do not con­nect this V- pin to ground or anoth­er volt­age or the 7660 will be dam­aged.Module Amplification / GainThe mod­ule accepts an AC or DC input sig­nal of between 100uV and 300mV.  The sig­nal is input on the S and S- pins.If the input is a ground ref­er­enced (sin­gle-end­ed) sig­nal, the sig­nal is con­nect­ed to S and sig­nal ground is con­nect­ed to S-.  Alter­na­tive­ly, a dif­fer­en­tial sig­nal such as from a bridge sen­sor can be input across the S and S- pins.The inputs have a 1K series resis­tor to lim­it input cur­rent to a safe lev­el.Gain of the AD620 is adjust­ed using a 100K poten­tiome­ter (marked 104).  The adver­tised gain is 1.5x to 1000x and a low­er resis­tance equals a high­er gain.  Turn­ing the pot CW increas­es the gain.The out­put of the AD620 is passed through one of the two LM358 op amps con­fig­ured as a uni­ty gain buffer.  The LM358 can source about 30mA and sink 20mA.  The out­put of this buffer is avail­able on the pin labeled VOUT.Zero Offset AdjustmentThe oth­er half of the LM358 is also set­up as a uni­ty gain buffer to feed the Vref input of the AD620.The input of the LM358 has a 10K poten­tiome­ter (marked 103) and series 1K resis­tor tied between the V and V- pow­er rails.  The poten­tiome­ter adjusts the volt­age input to the LM358 and the out­put is fed into the Vref pin on the AD620.  This allows any off­set to be adjust­ed out or if desired, a pos­i­tive or neg­a­tive off­set can be adjust­ed in.  Turn­ing the poten­tiome­ter CW increas­es the off­set in a pos­i­tive direc­tion.To set the off­set, the S and S- pins are short­ed togeth­er and the 10K zero off­set poten­tiome­ter is adjust­ed until the volt­age at VOUT mea­sures 0V or the desired amount of off­set.Module ConnectionsThe mod­ule has inputs on one end and out­puts on the oth­er.  These can be used to con­nect wires or head­er pins can be sol­dered in depend­ing on the appli­ca­tion.1×4 Input Head­erVIN = Mod­ule pow­er (3.5 to 10V)GND = Ground for mod­ule pow­erS- = Sig­nal Input (neg­a­tive con­nec­tion)S  = Sig­nal Input (pos­i­tive con­nec­tion)1×4 Out­put Head­erV- = Neg­a­tive volt­age out­put from 7660GND = GroundVOUT = Sig­nal Out­putGND = GroundThe dia­grams below show the basic con­nec­tion setups for sin­gle-end­ed and dif­fer­en­tial inputs as well as the set­up for adjust­ing the Zero Off­set.Documents :Datasheet.