= Solution
A representative bipolar-input 741 amplifier has \b[$R_{\rm in}$ of order $10^6\,\Omega$]; the LM741 specification gives a typical $2\,\mathrm{M\Omega}$ at $25^\circ\mathrm C$. This is an illustrative device specification, not an identification of an unspecified practical-class part. Other input architectures can have much larger <electrical resistance>, and finite input <capacitance> makes the <input impedance> <frequency> dependent.<LM741 Operational Amplifier by Texas Instruments>[SNOSC25D, §6.5, p. 5, input-resistance row and its test conditions]{ref}
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