/technologies/open-source-hardware/b/blog/posts/discrete-difference-amplifier---ac-analysis-gain-and-bandwidthThis is the AC gain and BW analysis of the difference amplifier module that shabaz designed for a Direct Conversion Receiver . I&#39;m searching for these points: gain at 1 kHz (approx. mid of bandwidth) -3 dB frequencies ...en-USTelligent Community 12https://community.element14.com/technologies/open-source-hardware/b/blog/posts/discrete-difference-amplifier---ac-analysis-gain-and-bandwidthMon, 20 Jul 2026 12:51:21 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:227467c7-bc63-4a2b-92f2-a14104882a78Jan Cumps0<ol> <li>&nbsp;IN1</li> <li>&nbsp;out</li> <li>&nbsp;Q4 collector</li> </ol> <p>conditions:</p> <ul> <li>V+: 9V</li> <li>IN1: sinus 1 kHz, 100 mV_rms&nbsp;</li> <li>IN2: ground</li> </ul> <p><img height="412" src="/resized-image/__size/998x824/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-227467c7-bc63-4a2b-92f2-a14104882a78/pastedimage1784551868782v1.png" width="499" alt=" " /></p><img src="https://community.element14.com/aggbug?PostID=29941&AppID=18&AppType=Weblog&ContentType=0" width="1" height="1">https://community.element14.com/technologies/open-source-hardware/b/blog/posts/discrete-difference-amplifier---ac-analysis-gain-and-bandwidthFri, 17 Jul 2026 09:10:44 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:227467c7-bc63-4a2b-92f2-a14104882a78Jan Cumps1<p>&nbsp;[mention:b0bc65b9ecdc4307bd967592f00e340a:e9ed411860ed4f2ba0265705b8793d05]&nbsp;, the current source in the tail of&nbsp;the differential amp (orange area below):</p> <p><img alt=" " height="639" src="/resized-image/__size/776x1278/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-227467c7-bc63-4a2b-92f2-a14104882a78/pastedimage1784279370743v1.png" width="388" /></p> <p>what was your inspiration to design that sub-circuit that way?</p><img src="https://community.element14.com/aggbug?PostID=29941&AppID=18&AppType=Weblog&ContentType=0" width="1" height="1">https://community.element14.com/technologies/open-source-hardware/b/blog/posts/discrete-difference-amplifier---ac-analysis-gain-and-bandwidthThu, 16 Jul 2026 09:57:30 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:227467c7-bc63-4a2b-92f2-a14104882a78Jan Cumps2<p>For the next blog, I plan to</p> <ul> <li>show some internal signals</li> <li>test how the circuit behaves when there is an identical signal on both inputs (desired/theoretical result: no output signal)</li> <li>go into the design, maybe based on Art of Electronics:</li> </ul> <p><img height="802" src="/resized-image/__size/722x1604/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-227467c7-bc63-4a2b-92f2-a14104882a78/1783368112672_5F00_0.jpg" width="361" alt=" " /></p><img src="https://community.element14.com/aggbug?PostID=29941&AppID=18&AppType=Weblog&ContentType=0" width="1" height="1">https://community.element14.com/technologies/open-source-hardware/b/blog/posts/discrete-difference-amplifier---ac-analysis-gain-and-bandwidthWed, 15 Jul 2026 11:39:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:227467c7-bc63-4a2b-92f2-a14104882a78shabaz0<p>Hi Jan,</p> <p>Very useful information!&nbsp;I had not got the stripboard prototype working too well (I probably made a soldering or component error somewhere) so it is great to see these real measurements with the PCB.</p><img src="https://community.element14.com/aggbug?PostID=29941&AppID=18&AppType=Weblog&ContentType=0" width="1" height="1">https://community.element14.com/technologies/open-source-hardware/b/blog/posts/discrete-difference-amplifier---ac-analysis-gain-and-bandwidthTue, 14 Jul 2026 20:45:16 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:227467c7-bc63-4a2b-92f2-a14104882a78DAB0<p>Very cool Jan.</p><img src="https://community.element14.com/aggbug?PostID=29941&AppID=18&AppType=Weblog&ContentType=0" width="1" height="1">